Python django.db.models.ManyToManyField() Examples

def get_required_fields(self, exclude_with_default=True):
        """
        Method to get all required fields for the linked content type model

        :param exclude_with_default: Whether or not to exclude fields with default values
        :type exclude_with_default: bool

        :return: List of required field names
        """
        def filter_field(field):
            if field.blank:
                return False
            elif isinstance(field, models.ManyToManyField):
                return False
            elif exclude_with_default and field.has_default():
                return False
            else:
                return True
        return list(filter(filter_field, self.get_model_fields())) 

def __set__(self, instance, value):
        if not self.related.field.rel.through._meta.auto_created:
            opts = self.related.field.rel.through._meta
            raise AttributeError(
                "Cannot set values on a ManyToManyField which specifies an "
                "intermediary model. Use %s.%s's Manager instead." % (opts.app_label, opts.object_name)
            )

        # Force evaluation of `value` in case it's a queryset whose
        # value could be affected by `manager.clear()`. Refs #19816.
        value = tuple(value)

        manager = self.__get__(instance)
        db = router.db_for_write(manager.through, instance=manager.instance)
        with transaction.atomic(using=db, savepoint=False):
            manager.clear()
            manager.add(*value) 

def __set__(self, instance, value):
        if not self.field.rel.through._meta.auto_created:
            opts = self.field.rel.through._meta
            raise AttributeError(
                "Cannot set values on a ManyToManyField which specifies an "
                "intermediary model.  Use %s.%s's Manager instead." % (opts.app_label, opts.object_name)
            )

        # Force evaluation of `value` in case it's a queryset whose
        # value could be affected by `manager.clear()`. Refs #19816.
        value = tuple(value)

        manager = self.__get__(instance)
        db = router.db_for_write(manager.through, instance=manager.instance)
        with transaction.atomic(using=db, savepoint=False):
            manager.clear()
            manager.add(*value) 

def _check_ignored_options(self, **kwargs):
        warnings = []

        if self.null:
            warnings.append(
                checks.Warning(
                    'null has no effect on ManyToManyField.',
                    hint=None,
                    obj=self,
                    id='fields.W340',
                )
            )

        if len(self._validators) > 0:
            warnings.append(
                checks.Warning(
                    'ManyToManyField does not support validators.',
                    hint=None,
                    obj=self,
                    id='fields.W341',
                )
            )

        return warnings 

def validate_list_display(self, cls, model):
        " Validate that list_display only contains fields or usable attributes. "
        if hasattr(cls, 'list_display'):
            check_isseq(cls, 'list_display', cls.list_display)
            for idx, field in enumerate(cls.list_display):
                if not callable(field):
                    if not hasattr(cls, field):
                        if not hasattr(model, field):
                            try:
                                model._meta.get_field(field)
                            except FieldDoesNotExist:
                                raise ImproperlyConfigured(
                                    "%s.list_display[%d], %r is not a callable or "
                                    "an attribute of %r or found in the model %r."
                                    % (cls.__name__, idx, field, cls.__name__, model._meta.object_name)
                                )
                        else:
                            # getattr(model, field) could be an X_RelatedObjectsDescriptor
                            f = fetch_attr(cls, model, "list_display[%d]" % idx, field)
                            if isinstance(f, models.ManyToManyField):
                                raise ImproperlyConfigured(
                                    "'%s.list_display[%d]', '%s' is a ManyToManyField "
                                    "which is not supported."
                                    % (cls.__name__, idx, field)
                                ) 

def _connect_signal(self, index):
        """Create signals for building indexes."""
        post_save_signal = ElasticSignal(index, 'build')
        post_save_signal.connect(post_save, sender=index.object_type)
        self.signals.append(post_save_signal)

        post_delete_signal = ElasticSignal(index, 'remove_object')
        post_delete_signal.connect(post_delete, sender=index.object_type)
        self.signals.append(post_delete_signal)

        # Connect signals for all dependencies.
        for dependency in index.get_dependencies():
            # Automatically convert m2m fields to dependencies.
            if isinstance(dependency, (models.ManyToManyField, ManyToManyDescriptor)):
                dependency = ManyToManyDependency(dependency)
            elif isinstance(dependency, ReverseManyToOneDescriptor):
                dependency = ReverseManyToOneDependency(dependency)
            elif isinstance(dependency, ForwardManyToOneDescriptor):
                dependency = ForwardManyToOneDependency(dependency)
            elif not isinstance(dependency, Dependency):
                raise TypeError("Unsupported dependency type: {}".format(repr(dependency)))

            signal = dependency.connect(index)
            self.signals.extend(signal) 

def _dict(self):
        exclude = ['operator_id', 'creator_id', 'created', 'modified']
        opts = self._meta
        data = {}
        keys = [f.attname for f in opts.fields]
        for f in chain(opts.many_to_many):
            #if isinstance(f, models.ManyToManyField):
            if self.pk is None:
                data[f.name] = []
            else:
                data[f.name] = list(f.value_from_object(self).values_list('pk', flat=True))
        original = { k:self.__dict__.get(k) for k in keys if k not in exclude }
        data.update(**original)
        for key, value in data.items():
            if isinstance(value, timezone.datetime):
                value = formats.localize(timezone.template_localtime(value))
            data.update(**{key: value})
        return data 

def formfield_for_manytomany(self, db_field, request=None, **kwargs):
        """
        Get a form Field for a ManyToManyField.
        """
        # If it uses an intermediary model that isn't auto created, don't show
        # a field in admin.
        if not db_field.rel.through._meta.auto_created:
            return None
        db = kwargs.get('using')

        if db_field.name in self.raw_id_fields:
            kwargs['widget'] = widgets.ManyToManyRawIdWidget(db_field.rel,
                                    self.admin_site, using=db)
            kwargs['help_text'] = ''
        elif db_field.name in (list(self.filter_vertical) + list(self.filter_horizontal)):
            kwargs['widget'] = widgets.FilteredSelectMultiple(db_field.verbose_name, (db_field.name in self.filter_vertical))

        queryset = self.get_field_queryset(db, db_field, request)
        if queryset is not None:
            kwargs['queryset'] = queryset

        return db_field.formfield(**kwargs) 

def validate_prepopulated_fields(self, cls, model):
        " Validate that prepopulated_fields if a dictionary  containing allowed field types. "
        # prepopulated_fields
        if hasattr(cls, 'prepopulated_fields'):
            check_isdict(cls, 'prepopulated_fields', cls.prepopulated_fields)
            for field, val in cls.prepopulated_fields.items():
                f = get_field(cls, model, 'prepopulated_fields', field)
                if isinstance(f, (models.DateTimeField, models.ForeignKey,
                    models.ManyToManyField)):
                    raise ImproperlyConfigured("'%s.prepopulated_fields['%s']' "
                            "is either a DateTimeField, ForeignKey or "
                            "ManyToManyField. This isn't allowed."
                            % (cls.__name__, field))
                check_isseq(cls, "prepopulated_fields['%s']" % field, val)
                for idx, f in enumerate(val):
                    get_field(cls, model, "prepopulated_fields['%s'][%d]" % (field, idx), f) 

def validate_list_display(self, cls, model):
        " Validate that list_display only contains fields or usable attributes. "
        if hasattr(cls, 'list_display'):
            check_isseq(cls, 'list_display', cls.list_display)
            for idx, field in enumerate(cls.list_display):
                if not callable(field):
                    if not hasattr(cls, field):
                        if not hasattr(model, field):
                            try:
                                model._meta.get_field(field)
                            except models.FieldDoesNotExist:
                                raise ImproperlyConfigured("%s.list_display[%d], %r is not a callable or an attribute of %r or found in the model %r."
                                    % (cls.__name__, idx, field, cls.__name__, model._meta.object_name))
                        else:
                            # getattr(model, field) could be an X_RelatedObjectsDescriptor
                            f = fetch_attr(cls, model, "list_display[%d]" % idx, field)
                            if isinstance(f, models.ManyToManyField):
                                raise ImproperlyConfigured("'%s.list_display[%d]', '%s' is a ManyToManyField which is not supported."
                                    % (cls.__name__, idx, field)) 

def _validate_field_name(self):
        field_names = self.model._meta.get_all_field_names()
        
        # If a custom name is provided, make sure the field exists on the model
        if self.__field_name is not None and self.__field_name not in field_names:
            raise ValueError("%s couldn't find a field named %s in %s." % \
                (self.__class__.__name__, self.__field_name, self.model._meta.object_name))
        
        # Otherwise, see if there is a field called either 'site' or 'sites'
        else:
            for potential_name in ['site', 'sites']:
                if potential_name in field_names:
                    self.__field_name = potential_name
                    self.__is_validated = True
                    break
        
        # Now do a type check on the field (FK or M2M only)
        try:
            field = self.model._meta.get_field(self.__field_name)
            if not isinstance(field, (models.ForeignKey, models.ManyToManyField)):
                raise TypeError("%s must be a ForeignKey or ManyToManyField." %self.__field_name)
        except FieldDoesNotExist:
            raise ValueError("%s couldn't find a field named %s in %s." % \
                    (self.__class__.__name__, self.__field_name, self.model._meta.object_name))
        self.__is_validated = True 

def __init__(self, to, db_constraint=True, swappable=True, **kwargs):
        try:
            to._meta
        except AttributeError:  # to._meta doesn't exist, so it must be RECURSIVE_RELATIONSHIP_CONSTANT
            assert isinstance(to, six.string_types), "%s(%r) is invalid. First parameter to ManyToManyField must be either a model, a model name, or the string %r" % (self.__class__.__name__, to, RECURSIVE_RELATIONSHIP_CONSTANT)
            # Class names must be ASCII in Python 2.x, so we forcibly coerce it here to break early if there's a problem.
            to = str(to)

        kwargs['verbose_name'] = kwargs.get('verbose_name', None)
        kwargs['rel'] = ManyToManyRel(to,
            related_name=kwargs.pop('related_name', None),
            related_query_name=kwargs.pop('related_query_name', None),
            limit_choices_to=kwargs.pop('limit_choices_to', None),
            symmetrical=kwargs.pop('symmetrical', to == RECURSIVE_RELATIONSHIP_CONSTANT),
            through=kwargs.pop('through', None),
            through_fields=kwargs.pop('through_fields', None),
            db_constraint=db_constraint,
        )

        self.swappable = swappable
        self.db_table = kwargs.pop('db_table', None)
        if kwargs['rel'].through is not None:
            assert self.db_table is None, "Cannot specify a db_table if an intermediary model is used."

        super(ManyToManyField, self).__init__(**kwargs) 

def _check_raw_id_fields_item(self, cls, model, field_name, label):
        """ Check an item of `raw_id_fields`, i.e. check that field named
        `field_name` exists in model `model` and is a ForeignKey or a
        ManyToManyField. """

        try:
            field = model._meta.get_field(field_name)
        except models.FieldDoesNotExist:
            return refer_to_missing_field(field=field_name, option=label,
                                          model=model, obj=cls, id='admin.E002')
        else:
            if not isinstance(field, (models.ForeignKey, models.ManyToManyField)):
                return must_be('a ForeignKey or ManyToManyField',
                               option=label, obj=cls, id='admin.E003')
            else:
                return [] 

def formfield_for_dbfield(self, db_field, **kwargs):
        # If it uses an intermediary model that isn't auto created, don't show
        # a field in admin.
        if isinstance(db_field, models.ManyToManyField) and not db_field.remote_field.through._meta.auto_created:
            return None

        attrs = self.get_field_attrs(db_field, **kwargs)
        return db_field.formfield(**dict(attrs, **kwargs)) 

def get_field_style(self, db_field, style, **kwargs):
        if style in ('radio', 'radio-inline') and (db_field.choices or isinstance(db_field, models.ForeignKey)):
            attrs = {'widget': widgets.AdminRadioSelect(
                attrs={'inline': 'inline' if style == 'radio-inline' else ''})}
            if db_field.choices:
                attrs['choices'] = db_field.get_choices(
                    include_blank=db_field.blank,
                    blank_choice=[('', _('Null'))]
                )
            return attrs

        if style in ('checkbox', 'checkbox-inline') and isinstance(db_field, models.ManyToManyField):
            return {'widget': widgets.AdminCheckboxSelect(attrs={'inline': style == 'checkbox-inline'}),
                    'help_text': None} 

def get_form_datas(self):
        # Prepare the dict of initial data from the request.
        # We have to special-case M2Ms as a list of comma-separated PKs.
        if self.request_method == 'get':
            initial = dict(self.request.GET.items())
            for k in initial:
                try:
                    f = self.opts.get_field(k)
                except models.FieldDoesNotExist:
                    continue
                if isinstance(f, models.ManyToManyField):
                    initial[k] = initial[k].split(",")
            return {'initial': initial}
        else:
            return {'data': self.request.POST, 'files': self.request.FILES} 

def get_field_style(self, attrs, db_field, style, **kwargs):
        if style == 'm2m_transfer' and isinstance(db_field, ManyToManyField):
            return {'widget': SelectMultipleTransfer(db_field.verbose_name, False), 'help_text': ''}
        if style == 'm2m_dropdown' and isinstance(db_field, ManyToManyField):
            return {'widget': SelectMultipleDropdown, 'help_text': ''}
        return attrs 

def formfield_for_dbfield(self, formfield, db_field, **kwargs):
        if formfield and self.model in self.admin_site._registry and isinstance(db_field, (models.ForeignKey, models.ManyToManyField)):
            rel_model = get_model_from_relation(db_field)
            if rel_model in self.admin_site._registry and self.has_model_perm(rel_model, 'add'):
                add_url = self.get_model_url(rel_model, 'add')
                formfield.widget = RelatedFieldWidgetWrapper(
                    formfield.widget, db_field.remote_field, add_url, self.get_model_url(self.model, 'add'))
        return formfield 

def formfield_for_dbfield(self, db_field, **kwargs):
        # If it uses an intermediary model that isn't auto created, don't show
        # a field in admin.
        if isinstance(db_field, models.ManyToManyField) and not db_field.rel.through._meta.auto_created:
            return None

        attrs = self.get_field_attrs(db_field, **kwargs)
        return db_field.formfield(**dict(attrs, **kwargs)) 

def get_field_style(self, db_field, style, **kwargs):
        if style in ('radio', 'radio-inline') and (db_field.choices or isinstance(db_field, models.ForeignKey)):
            attrs = {'widget': widgets.AdminRadioSelect(
                attrs={'inline': 'inline' if style == 'radio-inline' else ''})}
            if db_field.choices:
                attrs['choices'] = db_field.get_choices(
                    include_blank=db_field.blank,
                    blank_choice=[('', _('Null'))]
                )
            return attrs

        if style in ('checkbox', 'checkbox-inline') and isinstance(db_field, models.ManyToManyField):
            return {'widget': widgets.AdminCheckboxSelect(attrs={'inline': style == 'checkbox-inline'}),
                    'help_text': None} 

def get_form_datas(self):
        # Prepare the dict of initial data from the request.
        # We have to special-case M2Ms as a list of comma-separated PKs.
        if self.request_method == 'get':
            initial = dict(self.request.GET.items())
            for k in initial:
                try:
                    f = self.opts.get_field(k)
                except models.FieldDoesNotExist:
                    continue
                if isinstance(f, models.ManyToManyField):
                    initial[k] = initial[k].split(",")
            return {'initial': initial}
        else:
            return {'data': self.request.POST, 'files': self.request.FILES} 

def get_field_style(self, attrs, db_field, style, **kwargs):
        if style == 'm2m_transfer' and isinstance(db_field, ManyToManyField):
            return {'widget': SelectMultipleTransfer(db_field.verbose_name, False), 'help_text': ''}
        if style == 'm2m_dropdown' and isinstance(db_field, ManyToManyField):
            return {'widget': SelectMultipleDropdown, 'help_text': ''}
        return attrs 

def formfield_for_dbfield(self, formfield, db_field, **kwargs):
        if formfield and self.model in self.admin_site._registry and isinstance(db_field, (models.ForeignKey, models.ManyToManyField)):
            rel_model = get_model_from_relation(db_field)
            if rel_model in self.admin_site._registry and self.has_model_perm(rel_model, 'add'):
                add_url = self.get_model_url(rel_model, 'add')
                formfield.widget = RelatedFieldWidgetWrapper(
                    formfield.widget, db_field.rel, add_url, self.get_model_url(self.model, 'add'))
        return formfield 

def get_field_style(self, db_field, style, **kwargs):
        if style in ('radio', 'radio-inline') and (db_field.choices or isinstance(db_field, models.ForeignKey)):
            attrs = {'widget': widgets.AdminRadioSelect(
                attrs={'inline': 'inline' if style == 'radio-inline' else ''})}
            if db_field.choices:
                attrs['choices'] = db_field.get_choices(
                    include_blank=db_field.blank,
                    blank_choice=[('', _('Null'))]
                )
            return attrs

        if style in ('checkbox', 'checkbox-inline') and isinstance(db_field, models.ManyToManyField):
            return {'widget': widgets.AdminCheckboxSelect(attrs={'inline': style == 'checkbox-inline'}),
                    'help_text': None} 

def get_form_datas(self):
        # Prepare the dict of initial data from the request.
        # We have to special-case M2Ms as a list of comma-separated PKs.
        if self.request_method == 'get':
            initial = dict(self.request.GET.items())
            for k in initial:
                try:
                    f = self.opts.get_field(k)
                except models.FieldDoesNotExist:
                    continue
                if isinstance(f, models.ManyToManyField):
                    initial[k] = initial[k].split(",")
            return {'initial': initial}
        else:
            return {'data': self.request.POST, 'files': self.request.FILES} 

def get_field_style(self, attrs, db_field, style, **kwargs):
        if style == 'm2m_transfer' and isinstance(db_field, ManyToManyField):
            return {'widget': SelectMultipleTransfer(db_field.verbose_name, False), 'help_text': ''}
        if style == 'm2m_dropdown' and isinstance(db_field, ManyToManyField):
            return {'widget': SelectMultipleDropdown, 'help_text': ''}
        return attrs 

def formfield_for_dbfield(self, formfield, db_field, **kwargs):
        if formfield and self.model in self.admin_site._registry and isinstance(db_field, (models.ForeignKey, models.ManyToManyField)):
            rel_model = get_model_from_relation(db_field)
            if rel_model in self.admin_site._registry and self.has_model_perm(rel_model, 'add'):
                add_url = self.get_model_url(rel_model, 'add')
                formfield.widget = RelatedFieldWidgetWrapper(
                    formfield.widget, db_field.rel, add_url, self.get_model_url(self.model, 'add'))
        return formfield 

def formfield_for_dbfield(self, db_field, **kwargs):
        # If it uses an intermediary model that isn't auto created, don't show
        # a field in admin.
        if isinstance(db_field, models.ManyToManyField) and not db_field.remote_field.through._meta.auto_created:
            return None

        attrs = self.get_field_attrs(db_field, **kwargs)
        return db_field.formfield(**dict(attrs, **kwargs)) 

def get_form_datas(self):
        # Prepare the dict of initial data from the request.
        # We have to special-case M2Ms as a list of comma-separated PKs.
        if self.request_method == 'get':
            initial = dict(self.request.GET.items())
            for k in initial:
                try:
                    f = self.opts.get_field(k)
                except models.FieldDoesNotExist:
                    continue
                if isinstance(f, models.ManyToManyField):
                    initial[k] = initial[k].split(",")
            return {'initial': initial}
        else:
            return {'data': self.request.POST, 'files': self.request.FILES} 

def get_field_style(self, attrs, db_field, style, **kwargs):
        if style == 'm2m_transfer' and isinstance(db_field, ManyToManyField):
            return {'widget': SelectMultipleTransfer(db_field.verbose_name, False), 'help_text': ''}
        if style == 'm2m_dropdown' and isinstance(db_field, ManyToManyField):
            return {'widget': SelectMultipleDropdown, 'help_text': ''}
        return attrs 

def formfield_for_dbfield(self, formfield, db_field, **kwargs):
        if formfield and self.model in self.admin_site._registry and isinstance(db_field, (models.ForeignKey, models.ManyToManyField)):
            rel_model = get_model_from_relation(db_field)
            if rel_model in self.admin_site._registry and self.has_model_perm(rel_model, 'add'):
                add_url = self.get_model_url(rel_model, 'add')
                formfield.widget = RelatedFieldWidgetWrapper(
                    formfield.widget, db_field.remote_field, add_url, self.get_model_url(self.model, 'add'))
        return formfield 

def get_concrete_class_for_model_field(cls, model_field):
        """
        Method for getting a concrete model class to represent the type of form field required

        :param model_field: Model Field instance
        :return: OmniField subclass
        """
        field_mapping = {
            models.CharField: OmniCharField,
            models.TextField: OmniCharField,
            models.BooleanField: OmniBooleanField,
            models.NullBooleanField: OmniBooleanField,
            models.DateField: OmniDateField,
            models.DateTimeField: OmniDateTimeField,
            models.DecimalField: OmniDecimalField,
            models.EmailField: OmniEmailField,
            models.FloatField: OmniFloatField,
            models.IntegerField: OmniIntegerField,
            models.BigIntegerField: OmniIntegerField,
            models.PositiveIntegerField: OmniIntegerField,
            models.PositiveSmallIntegerField: OmniIntegerField,
            models.SmallIntegerField: OmniIntegerField,
            models.CommaSeparatedIntegerField: OmniCharField,
            models.TimeField: OmniTimeField,
            models.URLField: OmniUrlField,
            models.ForeignKey: OmniForeignKeyField,
            models.ManyToManyField: OmniManyToManyField,
            models.SlugField: OmniSlugField,
            models.FileField: OmniFileField,
            models.ImageField: OmniImageField,
            models.DurationField: OmniDurationField,
            models.GenericIPAddressField: OmniGenericIPAddressField
        }
        field_mapping.update(cls.get_custom_field_mapping())
        return field_mapping.get(model_field.__class__) 

def test_get_concrete_class_for_model_field(self):
        """
        The get_concrete_class_for_model_field method should return the correct OmniField subclass
        """
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.CharField()), OmniCharField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.NullBooleanField()), OmniBooleanField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.BooleanField()), OmniBooleanField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.DateTimeField()), OmniDateTimeField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.DecimalField()), OmniDecimalField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.EmailField()), OmniEmailField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.FloatField()), OmniFloatField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.IntegerField()), OmniIntegerField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.BigIntegerField()), OmniIntegerField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.PositiveIntegerField()), OmniIntegerField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.SmallIntegerField()), OmniIntegerField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.TimeField()), OmniTimeField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.URLField()), OmniUrlField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.SlugField()), OmniSlugField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.FileField()), OmniFileField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.ImageField()), OmniImageField)
        self.assertEqual(OmniField.get_concrete_class_for_model_field(models.DurationField()), OmniDurationField)
        self.assertEqual(
            OmniField.get_concrete_class_for_model_field(models.GenericIPAddressField()),
            OmniGenericIPAddressField
        )
        self.assertEqual(
            OmniField.get_concrete_class_for_model_field(models.CommaSeparatedIntegerField()),
            OmniCharField
        )
        self.assertEqual(
            OmniField.get_concrete_class_for_model_field(models.PositiveSmallIntegerField()),
            OmniIntegerField
        )
        self.assertEqual(
            OmniField.get_concrete_class_for_model_field(models.ForeignKey(DummyModel2)),
            OmniForeignKeyField
        )
        self.assertEqual(
            OmniField.get_concrete_class_for_model_field(models.ManyToManyField(DummyModel2)),
            OmniManyToManyField
        ) 

def save_and_check_for_duplicates(self):
        # FIXME: Cache summaries in the DB so this query is faster.
        duplicates = [citation for citation in
                      Citation.objects.filter(
                          portfolio_entry=self.portfolio_entry)
                      if (citation.pk != self.pk) and (citation.summary == self.summary)]

        if duplicates:
            self.ignored_due_to_duplicate = True
        return self.save()

    # [0]: FIXME: Let's learn how to use Django's ManyToManyField etc. 

def _field_val(self, obj, field):
        # choice fields
        if field.name in self._choice_list_map.keys():
            val = getattr(obj, field.name)
            return self._choice_list_map[field.name].get(val)

        # bit fields
        elif isinstance(field, BitField):
            val = getattr(obj, field.name)
            # val is instance of BitHandler
            return int(val)

        # image fields
        elif isinstance(field, ImageField):
            val = getattr(obj, field.name)
            return getattr(val, 'url') if val else None

        # mac address validated by netaddr.EUI
        elif isinstance(field, MACAddressField):
            val = getattr(obj, field.name)
            return str(val)

        # related fields
        if field.is_relation:
            if isinstance(field, ManyToOneRel):
                return getattr(obj, field.field_name)
            val = getattr(obj, field.attname)
            if isinstance(field, ManyToManyField):
                s = val.only('pk').values_list('pk', flat=True)
                return tuple(s)
            return val

        # all other simple fields
        else:
            v = getattr(obj, field.name)
            if isinstance(v, bool):
                return v
            if field.null:
                return v or None
            return v 

def _generate_added_field(self, app_label, model_name, field_name):
        field = self.new_apps.get_model(app_label, model_name)._meta.get_field(field_name)
        # Fields that are foreignkeys/m2ms depend on stuff
        dependencies = []
        if field.rel and field.rel.to:
            # Account for FKs to swappable models
            swappable_setting = getattr(field, 'swappable_setting', None)
            if swappable_setting is not None:
                dep_app_label = "__setting__"
                dep_object_name = swappable_setting
            else:
                dep_app_label = field.rel.to._meta.app_label
                dep_object_name = field.rel.to._meta.object_name
            dependencies = [(dep_app_label, dep_object_name, None, True)]
            if getattr(field.rel, "through", None) and not field.rel.through._meta.auto_created:
                dependencies.append((
                    field.rel.through._meta.app_label,
                    field.rel.through._meta.object_name,
                    None,
                    True,
                ))
        # You can't just add NOT NULL fields with no default or fields
        # which don't allow empty strings as default.
        preserve_default = True
        if (not field.null and not field.has_default() and
                not isinstance(field, models.ManyToManyField) and
                not (field.blank and field.empty_strings_allowed)):
            field = field.clone()
            field.default = self.questioner.ask_not_null_addition(field_name, model_name)
            preserve_default = False
        self.add_operation(
            app_label,
            operations.AddField(
                model_name=model_name,
                name=field_name,
                field=field,
                preserve_default=preserve_default,
            ),
            dependencies=dependencies,
        ) 

def __init__(self, to, db_constraint=True, swappable=True, **kwargs):
        try:
            to._meta
        except AttributeError:  # to._meta doesn't exist, so it must be RECURSIVE_RELATIONSHIP_CONSTANT
            assert isinstance(to, six.string_types), (
                "%s(%r) is invalid. First parameter to ManyToManyField must be "
                "either a model, a model name, or the string %r" %
                (self.__class__.__name__, to, RECURSIVE_RELATIONSHIP_CONSTANT)
            )
            # Class names must be ASCII in Python 2.x, so we forcibly coerce it
            # here to break early if there's a problem.
            to = str(to)
        kwargs['verbose_name'] = kwargs.get('verbose_name', None)
        kwargs['rel'] = ManyToManyRel(
            self, to,
            related_name=kwargs.pop('related_name', None),
            related_query_name=kwargs.pop('related_query_name', None),
            limit_choices_to=kwargs.pop('limit_choices_to', None),
            symmetrical=kwargs.pop('symmetrical', to == RECURSIVE_RELATIONSHIP_CONSTANT),
            through=kwargs.pop('through', None),
            through_fields=kwargs.pop('through_fields', None),
            db_constraint=db_constraint,
        )

        self.swappable = swappable
        self.db_table = kwargs.pop('db_table', None)
        if kwargs['rel'].through is not None:
            assert self.db_table is None, "Cannot specify a db_table if an intermediary model is used."

        super(ManyToManyField, self).__init__(**kwargs) 

def deconstruct(self):
        name, path, args, kwargs = super(ManyToManyField, self).deconstruct()
        # Handle the simpler arguments
        if self.db_table is not None:
            kwargs['db_table'] = self.db_table
        if self.rel.db_constraint is not True:
            kwargs['db_constraint'] = self.rel.db_constraint
        if self.rel.related_name is not None:
            kwargs['related_name'] = self.rel.related_name
        if self.rel.related_query_name is not None:
            kwargs['related_query_name'] = self.rel.related_query_name
        # Rel needs more work.
        if isinstance(self.rel.to, six.string_types):
            kwargs['to'] = self.rel.to
        else:
            kwargs['to'] = "%s.%s" % (self.rel.to._meta.app_label, self.rel.to._meta.object_name)
        if getattr(self.rel, 'through', None) is not None:
            if isinstance(self.rel.through, six.string_types):
                kwargs['through'] = self.rel.through
            elif not self.rel.through._meta.auto_created:
                kwargs['through'] = "%s.%s" % (self.rel.through._meta.app_label, self.rel.through._meta.object_name)
        # If swappable is True, then see if we're actually pointing to the target
        # of a swap.
        swappable_setting = self.swappable_setting
        if swappable_setting is not None:
            # If it's already a settings reference, error
            if hasattr(kwargs['to'], "setting_name"):
                if kwargs['to'].setting_name != swappable_setting:
                    raise ValueError(
                        "Cannot deconstruct a ManyToManyField pointing to a "
                        "model that is swapped in place of more than one model "
                        "(%s and %s)" % (kwargs['to'].setting_name, swappable_setting)
                    )
            # Set it
            from django.db.migrations.writer import SettingsReference
            kwargs['to'] = SettingsReference(
                kwargs['to'],
                swappable_setting,
            )
        return name, path, args, kwargs 

def contribute_to_class(self, cls, name, **kwargs):
        # To support multiple relations to self, it's useful to have a non-None
        # related name on symmetrical relations for internal reasons. The
        # concept doesn't make a lot of sense externally ("you want me to
        # specify *what* on my non-reversible relation?!"), so we set it up
        # automatically. The funky name reduces the chance of an accidental
        # clash.
        if self.rel.symmetrical and (self.rel.to == "self" or self.rel.to == cls._meta.object_name):
            self.rel.related_name = "%s_rel_+" % name

        super(ManyToManyField, self).contribute_to_class(cls, name, **kwargs)

        # The intermediate m2m model is not auto created if:
        #  1) There is a manually specified intermediate, or
        #  2) The class owning the m2m field is abstract.
        #  3) The class owning the m2m field has been swapped out.
        if not self.rel.through and not cls._meta.abstract and not cls._meta.swapped:
            self.rel.through = create_many_to_many_intermediary_model(self, cls)

        # Add the descriptor for the m2m relation
        setattr(cls, self.name, ReverseManyRelatedObjectsDescriptor(self))

        # Set up the accessor for the m2m table name for the relation
        self.m2m_db_table = curry(self._get_m2m_db_table, cls._meta)

        # Populate some necessary rel arguments so that cross-app relations
        # work correctly.
        if isinstance(self.rel.through, six.string_types):
            def resolve_through_model(field, model, cls):
                field.rel.through = model
            add_lazy_relation(cls, self, self.rel.through, resolve_through_model) 

def db_type(self, connection):
        # A ManyToManyField is not represented by a single column,
        # so return None.
        return None 

def _check_field_spec_item(self, cls, model, field_name, label):
        if field_name in cls.readonly_fields:
            # Stuff can be put in fields that isn't actually a model field if
            # it's in readonly_fields, readonly_fields will handle the
            # validation of such things.
            return []
        else:
            try:
                field = model._meta.get_field(field_name)
            except FieldDoesNotExist:
                # If we can't find a field on the model that matches, it could
                # be an extra field on the form.
                return []
            else:
                if (isinstance(field, models.ManyToManyField) and
                        not field.rel.through._meta.auto_created):
                    return [
                        checks.Error(
                            ("The value of '%s' cannot include the ManyToManyField '%s', "
                             "because that field manually specifies a relationship model.")
                            % (label, field_name),
                            hint=None,
                            obj=cls,
                            id='admin.E013',
                        )
                    ]
                else:
                    return [] 

def _check_filter_item(self, cls, model, field_name, label):
        """ Check one item of `filter_vertical` or `filter_horizontal`, i.e.
        check that given field exists and is a ManyToManyField. """

        try:
            field = model._meta.get_field(field_name)
        except FieldDoesNotExist:
            return refer_to_missing_field(field=field_name, option=label,
                                          model=model, obj=cls, id='admin.E019')
        else:
            if not isinstance(field, models.ManyToManyField):
                return must_be('a ManyToManyField', option=label, obj=cls, id='admin.E020')
            else:
                return [] 

def _check_prepopulated_fields_key(self, cls, model, field_name, label):
        """ Check a key of `prepopulated_fields` dictionary, i.e. check that it
        is a name of existing field and the field is one of the allowed types.
        """

        forbidden_field_types = (
            models.DateTimeField,
            models.ForeignKey,
            models.ManyToManyField
        )

        try:
            field = model._meta.get_field(field_name)
        except FieldDoesNotExist:
            return refer_to_missing_field(field=field_name, option=label,
                                          model=model, obj=cls, id='admin.E027')
        else:
            if isinstance(field, forbidden_field_types):
                return [
                    checks.Error(
                        "The value of '%s' refers to '%s', which must not be a DateTimeField, "
                        "ForeignKey or ManyToManyField." % (
                            label, field_name
                        ),
                        hint=None,
                        obj=cls,
                        id='admin.E028',
                    )
                ]
            else:
                return [] 

def get_changeform_initial_data(self, request):
        """
        Get the initial form data.
        Unless overridden, this populates from the GET params.
        """
        initial = dict(request.GET.items())
        for k in initial:
            try:
                f = self.model._meta.get_field(k)
            except FieldDoesNotExist:
                continue
            # We have to special-case M2Ms as a list of comma-separated PKs.
            if isinstance(f, models.ManyToManyField):
                initial[k] = initial[k].split(",")
        return initial 

def check_field_spec(self, cls, model, flds, label):
        """
        Validate the fields specification in `flds` from a ModelAdmin subclass
        `cls` for the `model` model. Use `label` for reporting problems to the user.

        The fields specification can be a ``fields`` option or a ``fields``
        sub-option from a ``fieldsets`` option component.
        """
        for fields in flds:
            # The entry in fields might be a tuple. If it is a standalone
            # field, make it into a tuple to make processing easier.
            if type(fields) != tuple:
                fields = (fields,)
            for field in fields:
                if field in cls.readonly_fields:
                    # Stuff can be put in fields that isn't actually a
                    # model field if it's in readonly_fields,
                    # readonly_fields will handle the validation of such
                    # things.
                    continue
                try:
                    f = model._meta.get_field(field)
                except FieldDoesNotExist:
                    # If we can't find a field on the model that matches, it could be an
                    # extra field on the form; nothing to check so move on to the next field.
                    continue
                if isinstance(f, models.ManyToManyField) and not f.rel.through._meta.auto_created:
                    raise ImproperlyConfigured("'%s.%s' "
                        "can't include the ManyToManyField field '%s' because "
                        "'%s' manually specifies a 'through' model." % (
                            cls.__name__, label, field, field)) 

def validate_raw_id_fields(self, cls, model):
        " Validate that raw_id_fields only contains field names that are listed on the model. "
        if hasattr(cls, 'raw_id_fields'):
            check_isseq(cls, 'raw_id_fields', cls.raw_id_fields)
            for idx, field in enumerate(cls.raw_id_fields):
                f = get_field(cls, model, 'raw_id_fields', field)
                if not isinstance(f, (models.ForeignKey, models.ManyToManyField)):
                    raise ImproperlyConfigured("'%s.raw_id_fields[%d]', '%s' must "
                            "be either a ForeignKey or ManyToManyField."
                            % (cls.__name__, idx, field)) 

def validate_filter_vertical(self, cls, model):
        " Validate that filter_vertical is a sequence of field names. "
        if hasattr(cls, 'filter_vertical'):
            check_isseq(cls, 'filter_vertical', cls.filter_vertical)
            for idx, field in enumerate(cls.filter_vertical):
                f = get_field(cls, model, 'filter_vertical', field)
                if not isinstance(f, models.ManyToManyField):
                    raise ImproperlyConfigured("'%s.filter_vertical[%d]' must be "
                        "a ManyToManyField." % (cls.__name__, idx)) 

def validate_filter_horizontal(self, cls, model):
        " Validate that filter_horizontal is a sequence of field names. "
        if hasattr(cls, 'filter_horizontal'):
            check_isseq(cls, 'filter_horizontal', cls.filter_horizontal)
            for idx, field in enumerate(cls.filter_horizontal):
                f = get_field(cls, model, 'filter_horizontal', field)
                if not isinstance(f, models.ManyToManyField):
                    raise ImproperlyConfigured("'%s.filter_horizontal[%d]' must be "
                        "a ManyToManyField." % (cls.__name__, idx)) 

def __enter__(self):
        self._old_au_local_m2m = AbstractUser._meta.local_many_to_many
        self._old_pm_local_m2m = PermissionsMixin._meta.local_many_to_many
        groups = models.ManyToManyField(Group, blank=True)
        groups.contribute_to_class(PermissionsMixin, "groups")
        user_permissions = models.ManyToManyField(Permission, blank=True)
        user_permissions.contribute_to_class(PermissionsMixin, "user_permissions")
        PermissionsMixin._meta.local_many_to_many = [groups, user_permissions]
        AbstractUser._meta.local_many_to_many = [groups, user_permissions] 

def normalize_relations(field):
	field_type = type(field)
	if field_type is models.ForeignKey:
		return 'ForeignKey({})'.format(get_rel_model(field).__name__)
	if field_type is models.ManyToManyField:
		return 'ManyToManyField({})'.format(get_rel_model(field).__name__)
	if field_type is models.OneToOneField:
		return 'OneToOneField({})'.format(get_rel_model(field).__name__)
	return None 

def formfield_for_dbfield(self, db_field, **kwargs):
        # If it uses an intermediary model that isn't auto created, don't show
        # a field in admin.
        if isinstance(db_field, models.ManyToManyField) and not db_field.rel.through._meta.auto_created:
            return None

        attrs = self.get_field_attrs(db_field, **kwargs)
        return db_field.formfield(**dict(attrs, **kwargs)) 

def get_field_style(self, db_field, style, **kwargs):
        if style in ('radio', 'radio-inline') and (db_field.choices or isinstance(db_field, models.ForeignKey)):
            attrs = {'widget': widgets.AdminRadioSelect(
                attrs={'inline': 'inline' if style == 'radio-inline' else ''})}
            if db_field.choices:
                attrs['choices'] = db_field.get_choices(
                    include_blank=db_field.blank,
                    blank_choice=[('', _('Null'))]
                )
            return attrs

        if style in ('checkbox', 'checkbox-inline') and isinstance(db_field, models.ManyToManyField):
            return {'widget': widgets.AdminCheckboxSelect(attrs={'inline': style == 'checkbox-inline'}),
                    'help_text': None} 

def get_form_datas(self):
        # Prepare the dict of initial data from the request.
        # We have to special-case M2Ms as a list of comma-separated PKs.
        if self.request_method == 'get':
            initial = dict(self.request.GET.items())
            for k in initial:
                try:
                    f = self.opts.get_field(k)
                except models.FieldDoesNotExist:
                    continue
                if isinstance(f, models.ManyToManyField):
                    initial[k] = initial[k].split(",")
            return {'initial': initial}
        else:
            return {'data': self.request.POST, 'files': self.request.FILES} 

def get_field_style(self, attrs, db_field, style, **kwargs):
        if style == 'm2m_transfer' and isinstance(db_field, ManyToManyField):
            return {'widget': SelectMultipleTransfer(db_field.verbose_name, False), 'help_text': ''}
        if style == 'm2m_dropdown' and isinstance(db_field, ManyToManyField):
            return {'widget': SelectMultipleDropdown, 'help_text': ''}
        return attrs 

def formfield_for_dbfield(self, formfield, db_field, **kwargs):
        if formfield and self.model in self.admin_site._registry and isinstance(db_field, (models.ForeignKey, models.ManyToManyField)):
            rel_model = get_model_from_relation(db_field)
            if rel_model in self.admin_site._registry and self.has_model_perm(rel_model, 'add'):
                add_url = self.get_model_url(rel_model, 'add')
                formfield.widget = RelatedFieldWidgetWrapper(
                    formfield.widget, db_field.rel, add_url, self.get_model_url(self.model, 'add'))
        return formfield 

def formfield_for_dbfield(self, db_field, **kwargs):
        # If it uses an intermediary model that isn't auto created, don't show
        # a field in admin.
        if isinstance(db_field, models.ManyToManyField) and not db_field.rel.through._meta.auto_created:
            return None

        attrs = self.get_field_attrs(db_field, **kwargs)
        return db_field.formfield(**dict(attrs, **kwargs)) 

def get_field_style(self, db_field, style, **kwargs):
        if style in ('radio', 'radio-inline') and (db_field.choices or isinstance(db_field, models.ForeignKey)):
            attrs = {'widget': widgets.AdminRadioSelect(
                attrs={'inline': 'inline' if style == 'radio-inline' else ''})}
            if db_field.choices:
                attrs['choices'] = db_field.get_choices(
                    include_blank=db_field.blank,
                    blank_choice=[('', _('Null'))]
                )
            return attrs

        if style in ('checkbox', 'checkbox-inline') and isinstance(db_field, models.ManyToManyField):
            return {'widget': widgets.AdminCheckboxSelect(attrs={'inline': style == 'checkbox-inline'}),
                    'help_text': None} 

def get_form_datas(self):
        # Prepare the dict of initial data from the request.
        # We have to special-case M2Ms as a list of comma-separated PKs.
        if self.request_method == 'get':
            initial = dict(self.request.GET.items())
            for k in initial:
                try:
                    f = self.opts.get_field(k)
                except models.FieldDoesNotExist:
                    continue
                if isinstance(f, models.ManyToManyField):
                    initial[k] = initial[k].split(",")
            return {'initial': initial}
        else:
            return {'data': self.request.POST, 'files': self.request.FILES} 

def get_field_style(self, attrs, db_field, style, **kwargs):
        if style == 'm2m_transfer' and isinstance(db_field, ManyToManyField):
            return {'widget': SelectMultipleTransfer(db_field.verbose_name, False), 'help_text': ''}
        if style == 'm2m_dropdown' and isinstance(db_field, ManyToManyField):
            return {'widget': SelectMultipleDropdown, 'help_text': ''}
        return attrs 

def formfield_for_dbfield(self, formfield, db_field, **kwargs):
        if formfield and self.model in self.admin_site._registry and isinstance(db_field, (models.ForeignKey, models.ManyToManyField)):
            rel_model = get_model_from_relation(db_field)
            if rel_model in self.admin_site._registry and self.has_model_perm(rel_model, 'add'):
                add_url = self.get_model_url(rel_model, 'add')
                formfield.widget = RelatedFieldWidgetWrapper(
                    formfield.widget, db_field.rel, add_url, self.get_model_url(self.model, 'add'))
        return formfield 

def _is_custom(self, model, **kwargs):
        fields = {field.name: field for field in model._meta.get_fields()}
        for name in kwargs:
            if not isinstance(fields[name], (ManyToManyField, ManyToManyRel)):
                return True
        return False 

def get_form_kwargs(self):
        kwargs = super(NewModelView, self).get_form_kwargs()
        params = self.request.GET.dict()
        mfields = [f.attname for f in self.opts.fields]
        for k in params.keys():
            if k in mfields:
                kwargs.update({k: params[k]})
        related_models = []
        for f in self.opts.get_fields():
            if isinstance(f, (models.ForeignKey, models.ManyToManyField)):
                if f.related_model:
                    related_models.append(f.related_model)
        if User in related_models:
            kwargs.update({'user': self.request.user})
        return kwargs 

def get_form_kwargs(self):
        kwargs = super(EditModelView, self).get_form_kwargs()
        params = self.request.GET.dict()
        mfields = [f.attname for f in self.opts.fields]
        for k in params.keys():
            if k in mfields:
                kwargs.update({k: params[k]})
        related_models = []
        for f in self.opts.get_fields():
            if isinstance(f, (models.ForeignKey, models.ManyToManyField)):
                if f.related_model:
                    related_models.append(f.related_model)
        if User in related_models:
            kwargs.update({'user': self.request.user})
        return kwargs 

def check_field_spec(self, cls, model, flds, label):
        """
        Validate the fields specification in `flds` from a ModelAdmin subclass
        `cls` for the `model` model. Use `label` for reporting problems to the user.

        The fields specification can be a ``fields`` option or a ``fields``
        sub-option from a ``fieldsets`` option component.
        """
        for fields in flds:
            # The entry in fields might be a tuple. If it is a standalone
            # field, make it into a tuple to make processing easier.
            if type(fields) != tuple:
                fields = (fields,)
            for field in fields:
                if field in cls.readonly_fields:
                    # Stuff can be put in fields that isn't actually a
                    # model field if it's in readonly_fields,
                    # readonly_fields will handle the validation of such
                    # things.
                    continue
                try:
                    f = model._meta.get_field(field)
                except models.FieldDoesNotExist:
                    # If we can't find a field on the model that matches, it could be an
                    # extra field on the form; nothing to check so move on to the next field.
                    continue
                if isinstance(f, models.ManyToManyField) and not f.rel.through._meta.auto_created:
                    raise ImproperlyConfigured("'%s.%s' "
                        "can't include the ManyToManyField field '%s' because "
                        "'%s' manually specifies a 'through' model." % (
                            cls.__name__, label, field, field)) 

def validate_raw_id_fields(self, cls, model):
        " Validate that raw_id_fields only contains field names that are listed on the model. "
        if hasattr(cls, 'raw_id_fields'):
            check_isseq(cls, 'raw_id_fields', cls.raw_id_fields)
            for idx, field in enumerate(cls.raw_id_fields):
                f = get_field(cls, model, 'raw_id_fields', field)
                if not isinstance(f, (models.ForeignKey, models.ManyToManyField)):
                    raise ImproperlyConfigured("'%s.raw_id_fields[%d]', '%s' must "
                            "be either a ForeignKey or ManyToManyField."
                            % (cls.__name__, idx, field)) 

def validate_filter_vertical(self, cls, model):
        " Validate that filter_vertical is a sequence of field names. "
        if hasattr(cls, 'filter_vertical'):
            check_isseq(cls, 'filter_vertical', cls.filter_vertical)
            for idx, field in enumerate(cls.filter_vertical):
                f = get_field(cls, model, 'filter_vertical', field)
                if not isinstance(f, models.ManyToManyField):
                    raise ImproperlyConfigured("'%s.filter_vertical[%d]' must be "
                        "a ManyToManyField." % (cls.__name__, idx)) 

def generate_altered_fields(self):
        """
        Fields that have been altered.
        """
        for app_label, model_name, field_name in sorted(self.old_field_keys.intersection(self.new_field_keys)):
            # Did the field change?
            old_model_name = self.renamed_models.get((app_label, model_name), model_name)
            old_field_name = self.renamed_fields.get((app_label, model_name, field_name), field_name)
            old_field = self.old_apps.get_model(app_label, old_model_name)._meta.get_field_by_name(old_field_name)[0]
            new_field = self.new_apps.get_model(app_label, model_name)._meta.get_field_by_name(field_name)[0]
            # Implement any model renames on relations; these are handled by RenameModel
            # so we need to exclude them from the comparison
            if hasattr(new_field, "rel") and getattr(new_field.rel, "to", None):
                rename_key = (
                    new_field.rel.to._meta.app_label,
                    new_field.rel.to._meta.object_name.lower(),
                )
                if rename_key in self.renamed_models:
                    new_field.rel.to = old_field.rel.to
            old_field_dec = self.deep_deconstruct(old_field)
            new_field_dec = self.deep_deconstruct(new_field)
            if old_field_dec != new_field_dec:
                preserve_default = True
                if (old_field.null and not new_field.null and not new_field.has_default() and
                        not isinstance(new_field, models.ManyToManyField)):
                    field = new_field.clone()
                    new_default = self.questioner.ask_not_null_alteration(field_name, model_name)
                    if new_default is not models.NOT_PROVIDED:
                        field.default = new_default
                        preserve_default = False
                else:
                    field = new_field
                self.add_operation(
                    app_label,
                    operations.AlterField(
                        model_name=model_name,
                        name=field_name,
                        field=field,
                        preserve_default=preserve_default,
                    )
                ) 

def __set__(self, instance, value):
        if not self.related.field.rel.through._meta.auto_created:
            opts = self.related.field.rel.through._meta
            raise AttributeError("Cannot set values on a ManyToManyField which specifies an intermediary model. Use %s.%s's Manager instead." % (opts.app_label, opts.object_name))

        manager = self.__get__(instance)
        manager.clear()
        manager.add(*value) 

def __set__(self, instance, value):
        if not self.field.rel.through._meta.auto_created:
            opts = self.field.rel.through._meta
            raise AttributeError("Cannot set values on a ManyToManyField which specifies an intermediary model.  Use %s.%s's Manager instead." % (opts.app_label, opts.object_name))

        manager = self.__get__(instance)
        # clear() can change expected output of 'value' queryset, we force evaluation
        # of queryset before clear; ticket #19816
        value = tuple(value)
        manager.clear()
        manager.add(*value) 

def deconstruct(self):
        name, path, args, kwargs = super(ManyToManyField, self).deconstruct()
        # Handle the simpler arguments
        if self.db_table is not None:
            kwargs['db_table'] = self.db_table
        if self.rel.db_constraint is not True:
            kwargs['db_constraint'] = self.rel.db_constraint
        if self.rel.related_name is not None:
            kwargs['related_name'] = self.rel.related_name
        if self.rel.related_query_name is not None:
            kwargs['related_query_name'] = self.rel.related_query_name
        # Rel needs more work.
        if isinstance(self.rel.to, six.string_types):
            kwargs['to'] = self.rel.to
        else:
            kwargs['to'] = "%s.%s" % (self.rel.to._meta.app_label, self.rel.to._meta.object_name)
        if getattr(self.rel, 'through', None) is not None:
            if isinstance(self.rel.through, six.string_types):
                kwargs['through'] = self.rel.through
            elif not self.rel.through._meta.auto_created:
                kwargs['through'] = "%s.%s" % (self.rel.through._meta.app_label, self.rel.through._meta.object_name)
        # If swappable is True, then see if we're actually pointing to the target
        # of a swap.
        swappable_setting = self.swappable_setting
        if swappable_setting is not None:
            # If it's already a settings reference, error
            if hasattr(kwargs['to'], "setting_name"):
                if kwargs['to'].setting_name != swappable_setting:
                    raise ValueError("Cannot deconstruct a ManyToManyField pointing to a model that is swapped in place of more than one model (%s and %s)" % (kwargs['to'].setting_name, swappable_setting))
            # Set it
            from django.db.migrations.writer import SettingsReference
            kwargs['to'] = SettingsReference(
                kwargs['to'],
                swappable_setting,
            )
        return name, path, args, kwargs 

def contribute_to_class(self, cls, name):
        # To support multiple relations to self, it's useful to have a non-None
        # related name on symmetrical relations for internal reasons. The
        # concept doesn't make a lot of sense externally ("you want me to
        # specify *what* on my non-reversible relation?!"), so we set it up
        # automatically. The funky name reduces the chance of an accidental
        # clash.
        if self.rel.symmetrical and (self.rel.to == "self" or self.rel.to == cls._meta.object_name):
            self.rel.related_name = "%s_rel_+" % name

        super(ManyToManyField, self).contribute_to_class(cls, name)

        # The intermediate m2m model is not auto created if:
        #  1) There is a manually specified intermediate, or
        #  2) The class owning the m2m field is abstract.
        #  3) The class owning the m2m field has been swapped out.
        if not self.rel.through and not cls._meta.abstract and not cls._meta.swapped:
            self.rel.through = create_many_to_many_intermediary_model(self, cls)

        # Add the descriptor for the m2m relation
        setattr(cls, self.name, ReverseManyRelatedObjectsDescriptor(self))

        # Set up the accessor for the m2m table name for the relation
        self.m2m_db_table = curry(self._get_m2m_db_table, cls._meta)

        # Populate some necessary rel arguments so that cross-app relations
        # work correctly.
        if isinstance(self.rel.through, six.string_types):
            def resolve_through_model(field, model, cls):
                field.rel.through = model
            add_lazy_relation(cls, self, self.rel.through, resolve_through_model) 

def formfield(self, **kwargs):
        db = kwargs.pop('using', None)
        defaults = {
            'form_class': forms.ModelMultipleChoiceField,
            'queryset': self.rel.to._default_manager.using(db),
        }
        defaults.update(kwargs)
        # If initial is passed in, it's a list of related objects, but the
        # MultipleChoiceField takes a list of IDs.
        if defaults.get('initial') is not None:
            initial = defaults['initial']
            if callable(initial):
                initial = initial()
            defaults['initial'] = [i._get_pk_val() for i in initial]
        return super(ManyToManyField, self).formfield(**defaults) 

def db_type(self, connection):
        # A ManyToManyField is not represented by a single column,
        # so return None.
        return None 

def _check_filter_item(self, cls, model, field_name, label):
        """ Check one item of `filter_vertical` or `filter_horizontal`, i.e.
        check that given field exists and is a ManyToManyField. """

        try:
            field = model._meta.get_field(field_name)
        except models.FieldDoesNotExist:
            return refer_to_missing_field(field=field_name, option=label,
                                          model=model, obj=cls, id='admin.E019')
        else:
            if not isinstance(field, models.ManyToManyField):
                return must_be('a ManyToManyField', option=label, obj=cls, id='admin.E020')
            else:
                return [] 

def generate_altered_fields(self):
        """
        Fields that have been altered.
        """
        for app_label, model_name, field_name in sorted(self.old_field_keys.intersection(self.new_field_keys)):
            # Did the field change?
            old_model_name = self.renamed_models.get((app_label, model_name), model_name)
            old_field_name = self.renamed_fields.get((app_label, model_name, field_name), field_name)
            old_field = self.old_apps.get_model(app_label, old_model_name)._meta.get_field(old_field_name)
            new_field = self.new_apps.get_model(app_label, model_name)._meta.get_field(field_name)
            # Implement any model renames on relations; these are handled by RenameModel
            # so we need to exclude them from the comparison
            if hasattr(new_field, "rel") and getattr(new_field.rel, "to", None):
                rename_key = (
                    new_field.rel.to._meta.app_label,
                    new_field.rel.to._meta.model_name,
                )
                if rename_key in self.renamed_models:
                    new_field.rel.to = old_field.rel.to
            old_field_dec = self.deep_deconstruct(old_field)
            new_field_dec = self.deep_deconstruct(new_field)
            if old_field_dec != new_field_dec:
                both_m2m = (
                    isinstance(old_field, models.ManyToManyField) and
                    isinstance(new_field, models.ManyToManyField)
                )
                neither_m2m = (
                    not isinstance(old_field, models.ManyToManyField) and
                    not isinstance(new_field, models.ManyToManyField)
                )
                if both_m2m or neither_m2m:
                    # Either both fields are m2m or neither is
                    preserve_default = True
                    if (old_field.null and not new_field.null and not new_field.has_default() and
                            not isinstance(new_field, models.ManyToManyField)):
                        field = new_field.clone()
                        new_default = self.questioner.ask_not_null_alteration(field_name, model_name)
                        if new_default is not models.NOT_PROVIDED:
                            field.default = new_default
                            preserve_default = False
                    else:
                        field = new_field
                    self.add_operation(
                        app_label,
                        operations.AlterField(
                            model_name=model_name,
                            name=field_name,
                            field=field,
                            preserve_default=preserve_default,
                        )
                    )
                else:
                    # We cannot alter between m2m and concrete fields
                    self._generate_removed_field(app_label, model_name, field_name)
                    self._generate_added_field(app_label, model_name, field_name) 

def formfield(self, **kwargs):
        db = kwargs.pop('using', None)
        defaults = {
            'form_class': forms.ModelMultipleChoiceField,
            'queryset': self.rel.to._default_manager.using(db),
        }
        defaults.update(kwargs)
        # If initial is passed in, it's a list of related objects, but the
        # MultipleChoiceField takes a list of IDs.
        if defaults.get('initial') is not None:
            initial = defaults['initial']
            if callable(initial):
                initial = initial()
            defaults['initial'] = [i._get_pk_val() for i in initial]
        return super(ManyToManyField, self).formfield(**defaults) 

def _check_list_display_item(self, cls, model, item, label):
        if callable(item):
            return []
        elif hasattr(cls, item):
            return []
        elif hasattr(model, item):
            # getattr(model, item) could be an X_RelatedObjectsDescriptor
            try:
                field = model._meta.get_field(item)
            except FieldDoesNotExist:
                try:
                    field = getattr(model, item)
                except AttributeError:
                    field = None

            if field is None:
                return [
                    checks.Error(
                        "The value of '%s' refers to '%s', which is not a "
                        "callable, an attribute of '%s', or an attribute or method on '%s.%s'." % (
                            label, item, cls.__name__, model._meta.app_label, model._meta.object_name
                        ),
                        hint=None,
                        obj=cls,
                        id='admin.E108',
                    )
                ]
            elif isinstance(field, models.ManyToManyField):
                return [
                    checks.Error(
                        "The value of '%s' must not be a ManyToManyField." % label,
                        hint=None,
                        obj=cls,
                        id='admin.E109',
                    )
                ]
            else:
                return []
        else:
            try:
                model._meta.get_field(item)
            except FieldDoesNotExist:
                return [
                    # This is a deliberate repeat of E108; there's more than one path
                    # required to test this condition.
                    checks.Error(
                        "The value of '%s' refers to '%s', which is not a callable, "
                        "an attribute of '%s', or an attribute or method on '%s.%s'." % (
                            label, item, cls.__name__, model._meta.app_label, model._meta.object_name
                        ),
                        hint=None,
                        obj=cls,
                        id='admin.E108',
                    )
                ]
            else:
                return [] 

def formfield_for_dbfield(self, db_field, **kwargs):
        """
        Hook for specifying the form Field instance for a given database Field
        instance.

        If kwargs are given, they're passed to the form Field's constructor.
        """
        request = kwargs.pop("request", None)

        # If the field specifies choices, we don't need to look for special
        # admin widgets - we just need to use a select widget of some kind.
        if db_field.choices:
            return self.formfield_for_choice_field(db_field, request, **kwargs)

        # ForeignKey or ManyToManyFields
        if isinstance(db_field, (models.ForeignKey, models.ManyToManyField)):
            # Combine the field kwargs with any options for formfield_overrides.
            # Make sure the passed in **kwargs override anything in
            # formfield_overrides because **kwargs is more specific, and should
            # always win.
            if db_field.__class__ in self.formfield_overrides:
                kwargs = dict(self.formfield_overrides[db_field.__class__], **kwargs)

            # Get the correct formfield.
            if isinstance(db_field, models.ForeignKey):
                formfield = self.formfield_for_foreignkey(db_field, request, **kwargs)
            elif isinstance(db_field, models.ManyToManyField):
                formfield = self.formfield_for_manytomany(db_field, request, **kwargs)

            # For non-raw_id fields, wrap the widget with a wrapper that adds
            # extra HTML -- the "add other" interface -- to the end of the
            # rendered output. formfield can be None if it came from a
            # OneToOneField with parent_link=True or a M2M intermediary.
            if formfield and db_field.name not in self.raw_id_fields:
                related_modeladmin = self.admin_site._registry.get(db_field.rel.to)
                wrapper_kwargs = {}
                if related_modeladmin:
                    wrapper_kwargs.update(
                        can_add_related=related_modeladmin.has_add_permission(request),
                        can_change_related=related_modeladmin.has_change_permission(request),
                        can_delete_related=related_modeladmin.has_delete_permission(request),
                    )
                formfield.widget = widgets.RelatedFieldWidgetWrapper(
                    formfield.widget, db_field.rel, self.admin_site, **wrapper_kwargs
                )

            return formfield

        # If we've got overrides for the formfield defined, use 'em. **kwargs
        # passed to formfield_for_dbfield override the defaults.
        for klass in db_field.__class__.mro():
            if klass in self.formfield_overrides:
                kwargs = dict(copy.deepcopy(self.formfield_overrides[klass]), **kwargs)
                return db_field.formfield(**kwargs)

        # For any other type of field, just call its formfield() method.
        return db_field.formfield(**kwargs) 

def formfield_for_dbfield(self, db_field, **kwargs):
        """
        Hook for specifying the form Field instance for a given database Field
        instance.

        If kwargs are given, they're passed to the form Field's constructor.
        """
        request = kwargs.pop("request", None)

        # If the field specifies choices, we don't need to look for special
        # admin widgets - we just need to use a select widget of some kind.
        if db_field.choices:
            return self.formfield_for_choice_field(db_field, request, **kwargs)

        # ForeignKey or ManyToManyFields
        if isinstance(db_field, (models.ForeignKey, models.ManyToManyField)):
            # Combine the field kwargs with any options for formfield_overrides.
            # Make sure the passed in **kwargs override anything in
            # formfield_overrides because **kwargs is more specific, and should
            # always win.
            if db_field.__class__ in self.formfield_overrides:
                kwargs = dict(self.formfield_overrides[db_field.__class__], **kwargs)

            # Get the correct formfield.
            if isinstance(db_field, models.ForeignKey):
                formfield = self.formfield_for_foreignkey(db_field, request, **kwargs)
            elif isinstance(db_field, models.ManyToManyField):
                formfield = self.formfield_for_manytomany(db_field, request, **kwargs)

            # For non-raw_id fields, wrap the widget with a wrapper that adds
            # extra HTML -- the "add other" interface -- to the end of the
            # rendered output. formfield can be None if it came from a
            # OneToOneField with parent_link=True or a M2M intermediary.
            if formfield and db_field.name not in self.raw_id_fields:
                related_modeladmin = self.admin_site._registry.get(
                                                            db_field.rel.to)
                can_add_related = bool(related_modeladmin and
                            related_modeladmin.has_add_permission(request))
                formfield.widget = widgets.RelatedFieldWidgetWrapper(
                            formfield.widget, db_field.rel, self.admin_site,
                            can_add_related=can_add_related)

            return formfield

        # If we've got overrides for the formfield defined, use 'em. **kwargs
        # passed to formfield_for_dbfield override the defaults.
        for klass in db_field.__class__.mro():
            if klass in self.formfield_overrides:
                kwargs = dict(copy.deepcopy(self.formfield_overrides[klass]), **kwargs)
                return db_field.formfield(**kwargs)

        # For any other type of field, just call its formfield() method.
        return db_field.formfield(**kwargs) 

def generate_added_fields(self):
        """
        Fields that have been added
        """
        for app_label, model_name, field_name in sorted(self.new_field_keys - self.old_field_keys):
            field = self.new_apps.get_model(app_label, model_name)._meta.get_field_by_name(field_name)[0]
            # Fields that are foreignkeys/m2ms depend on stuff
            dependencies = []
            if field.rel and field.rel.to:
                # Account for FKs to swappable models
                swappable_setting = getattr(field, 'swappable_setting', None)
                if swappable_setting is not None:
                    dep_app_label = "__setting__"
                    dep_object_name = swappable_setting
                else:
                    dep_app_label = field.rel.to._meta.app_label
                    dep_object_name = field.rel.to._meta.object_name
                dependencies = [(dep_app_label, dep_object_name, None, True)]
                if getattr(field.rel, "through", None) and not field.rel.through._meta.auto_created:
                    dependencies.append((
                        field.rel.through._meta.app_label,
                        field.rel.through._meta.object_name,
                        None,
                        True
                    ))
            # You can't just add NOT NULL fields with no default or fields
            # which don't allow empty strings as default.
            if (not field.null and not field.has_default() and
                    not isinstance(field, models.ManyToManyField) and
                    not (field.blank and field.empty_strings_allowed)):
                field = field.clone()
                field.default = self.questioner.ask_not_null_addition(field_name, model_name)
                self.add_operation(
                    app_label,
                    operations.AddField(
                        model_name=model_name,
                        name=field_name,
                        field=field,
                        preserve_default=False,
                    ),
                    dependencies=dependencies,
                )
            else:
                self.add_operation(
                    app_label,
                    operations.AddField(
                        model_name=model_name,
                        name=field_name,
                        field=field,
                    ),
                    dependencies=dependencies,
                )