Python django.db.models.ForeignKey() Examples

def verify_fk(self, feat, rel_model, rel_mapping):
        """
        Given an OGR Feature, the related model and its dictionary mapping,
        this routine will retrieve the related model for the ForeignKey
        mapping.
        """
        # TODO: It is expensive to retrieve a model for every record --
        #  explore if an efficient mechanism exists for caching related
        #  ForeignKey models.

        # Constructing and verifying the related model keyword arguments.
        fk_kwargs = {}
        for field_name, ogr_name in rel_mapping.items():
            fk_kwargs[field_name] = self.verify_ogr_field(feat[ogr_name], rel_model._meta.get_field(field_name))

        # Attempting to retrieve and return the related model.
        try:
            return rel_model.objects.using(self.using).get(**fk_kwargs)
        except ObjectDoesNotExist:
            raise MissingForeignKey(
                'No ForeignKey %s model found with keyword arguments: %s' %
                (rel_model.__name__, fk_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 deconstruct(self):
        name, path, args, kwargs = super(ForeignKey, self).deconstruct()
        del kwargs['to_fields']
        del kwargs['from_fields']
        # Handle the simpler arguments
        if self.db_index:
            del kwargs['db_index']
        else:
            kwargs['db_index'] = False
        if self.db_constraint is not True:
            kwargs['db_constraint'] = self.db_constraint
        # Rel needs more work.
        to_meta = getattr(self.rel.to, "_meta", None)
        if self.rel.field_name and (not to_meta or (to_meta.pk and self.rel.field_name != to_meta.pk.name)):
            kwargs['to_field'] = self.rel.field_name
        return name, path, args, kwargs 

def forwards(self, orm):
        # Adding model 'Project'
        db.create_table('api_project', (
            ('id', self.gf('django.db.models.fields.AutoField')(primary_key=True)),
            ('name', self.gf('django.db.models.fields.CharField')(max_length=255)),
            ('organization', self.gf('django.db.models.fields.related.ForeignKey')(related_name='project_organization', to=orm['auth.User'])),
            ('created_by', self.gf('django.db.models.fields.related.ForeignKey')(related_name='project_creator', to=orm['auth.User'])),
            ('date_created', self.gf('django.db.models.fields.DateTimeField')(auto_now_add=True, blank=True)),
            ('date_modified', self.gf('django.db.models.fields.DateTimeField')(auto_now=True, blank=True)),
        ))
        db.send_create_signal('api', ['Project'])

        # Adding unique constraint on 'Project', fields ['name', 'organization']
        db.create_unique('api_project', ['name', 'organization_id'])

        # Adding M2M table for field projects on 'Team'
        db.create_table('api_team_projects', (
            ('id', models.AutoField(verbose_name='ID', primary_key=True, auto_created=True)),
            ('team', models.ForeignKey(orm['api.team'], null=False)),
            ('project', models.ForeignKey(orm['api.project'], null=False))
        ))
        db.create_unique('api_team_projects', ['team_id', 'project_id']) 

def validate(self, value, model_instance):
        if self.rel.parent_link:
            return
        super(ForeignKey, self).validate(value, model_instance)
        if value is None:
            return

        using = router.db_for_read(model_instance.__class__, instance=model_instance)
        qs = self.rel.to._default_manager.using(using).filter(
            **{self.rel.field_name: value}
        )
        qs = qs.complex_filter(self.get_limit_choices_to())
        if not qs.exists():
            raise exceptions.ValidationError(
                self.error_messages['invalid'],
                code='invalid',
                params={
                    'model': self.rel.to._meta.verbose_name, 'pk': value,
                    'field': self.rel.field_name, 'value': value,
                },  # 'pk' is included for backwards compatibility
            ) 

def has_perm(self, user, permission):
    if user.is_superuser:
        return True
    if isinstance(permission, six.string_types):
        permission = [permission, ]
    if user.has_perms(permission):
        return True
    if self._authorization_meta.owner_field and self._authorization_meta.owner_permission and \
       self._authorization_meta.owner_permission in permission and \
       user.pk == getattr(self, self._authorization_meta.owner_field).pk:
        return True
    paths = self._authorization_meta.model.get_authorization_paths(user, permission)
    if not paths.count():
        return False
    for field in self._authorization_meta.fields:
        f = self._meta.get_field(field)
        relation = getattr(self, field)
        if isinstance(f, models.ManyToManyField):
            qs_filter = reduce(lambda x, y: x | y, [Q(path__startswith=path) for path in paths])
            if relation.filter(qs_filter).distinct().exists():
                return True
        elif isinstance(f, models.ForeignKey):
            if relation is not None and any(relation.path.startswith(p) for p in paths):
                return True
    return False 

def _check_raw_id_fields_item(self, obj, 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 FieldDoesNotExist:
            return refer_to_missing_field(field=field_name, option=label,
                                          model=model, obj=obj, id='admin.E002')
        else:
            if not field.many_to_many and not isinstance(field, models.ForeignKey):
                return must_be('a foreign key or a many-to-many field',
                               option=label, obj=obj, id='admin.E003')
            else:
                return [] 

def _check_radio_fields_key(self, obj, model, field_name, label):
        """ Check that a key of `radio_fields` dictionary is name of existing
        field and that the field is a ForeignKey or has `choices` defined. """

        try:
            field = model._meta.get_field(field_name)
        except FieldDoesNotExist:
            return refer_to_missing_field(field=field_name, option=label,
                                          model=model, obj=obj, id='admin.E022')
        else:
            if not (isinstance(field, models.ForeignKey) or field.choices):
                return [
                    checks.Error(
                        "The value of '%s' refers to '%s', which is not an "
                        "instance of ForeignKey, and does not have a 'choices' definition." % (
                            label, field_name
                        ),
                        obj=obj.__class__,
                        id='admin.E023',
                    )
                ]
            else:
                return [] 

def formfield_for_foreignkey(self, db_field, request, **kwargs):
        """
        Get a form Field for a ForeignKey.
        """
        db = kwargs.get('using')

        if db_field.name in self.get_autocomplete_fields(request):
            kwargs['widget'] = AutocompleteSelect(db_field.remote_field, self.admin_site, using=db)
        elif db_field.name in self.raw_id_fields:
            kwargs['widget'] = widgets.ForeignKeyRawIdWidget(db_field.remote_field, self.admin_site, using=db)
        elif db_field.name in self.radio_fields:
            kwargs['widget'] = widgets.AdminRadioSelect(attrs={
                'class': get_ul_class(self.radio_fields[db_field.name]),
            })
            kwargs['empty_label'] = _('None') if db_field.blank else None

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

        return db_field.formfield(**kwargs) 

def allow_search_fields(cls, exclude=None):
    opts = cls._meta
    if not exclude:
        exclude = ['onidc', 'slug', 'created', 'modified']
    exclude.extend([f.name for f in opts.fields if getattr(f, 'choices')])
    fields = []
    for f in opts.fields:
        if exclude and f.name in exclude:
            continue
        if isinstance(f, models.ForeignKey):
            submodel = f.related_model
            for sub in submodel._meta.fields:
                if exclude and sub.name in exclude:
                    continue
                if isinstance(sub, models.CharField) \
                        and not getattr(sub, 'choices'):
                    fields.append(f.name + '__' + sub.name + '__icontains')
        if isinstance(f, models.CharField):
            fields.append(f.name + '__icontains')
    return fields 

def verify_fk(self, feat, rel_model, rel_mapping):
        """
        Given an OGR Feature, the related model and its dictionary mapping,
        retrieve the related model for the ForeignKey mapping.
        """
        # TODO: It is expensive to retrieve a model for every record --
        #  explore if an efficient mechanism exists for caching related
        #  ForeignKey models.

        # Constructing and verifying the related model keyword arguments.
        fk_kwargs = {}
        for field_name, ogr_name in rel_mapping.items():
            fk_kwargs[field_name] = self.verify_ogr_field(feat[ogr_name], rel_model._meta.get_field(field_name))

        # Attempting to retrieve and return the related model.
        try:
            return rel_model.objects.using(self.using).get(**fk_kwargs)
        except ObjectDoesNotExist:
            raise MissingForeignKey(
                'No ForeignKey %s model found with keyword arguments: %s' %
                (rel_model.__name__, fk_kwargs)
            ) 

def _get_field_type(field):
    if isinstance(field, models.ForeignKey):
        if django.VERSION >= (2, 0):
            to = field.remote_field.model
            if isinstance(to, str):
                to = _resolve_model(field, to)
        else:
            to = field.rel.to
            if isinstance(to, str):
                to = _resolve_model(field, to)

        return u":type %s: %s to :class:`~%s.%s`" % (
            field.name,
            type(field).__name__,
            to.__module__,
            to.__name__,
        )
    else:
        return u":type %s: %s" % (field.name, type(field).__name__) 

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 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 test_model_init_params(self):
        """Model __init__ gets all fields as params."""
        lines = []
        docstrings._add_model_fields_as_params(self.app, SimpleModel, lines)
        self.assertEqual(
            lines,
            [
                ":param id: Id",
                ":type id: AutoField",
                ":param user: User",
                ":type user: ForeignKey to :class:`~django.contrib.auth.models.User`",
                ":param user2: User2",
                ":type user2: ForeignKey to"
                " :class:`~sphinxcontrib_django.tests.test_docstrings.User2`",
                ":param user3: User3",
                ":type user3: ForeignKey to :class:`~django.contrib.auth.models.User`",
                ":param dummy_field: Dummy field",
                ":type dummy_field: CharField",
            ],
        ) 

def _check_radio_fields_key(self, cls, model, field_name, label):
        """ Check that a key of `radio_fields` dictionary is name of existing
        field and that the field is a ForeignKey or has `choices` defined. """

        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.E022')
        else:
            if not (isinstance(field, models.ForeignKey) or field.choices):
                return [
                    checks.Error(
                        "The value of '%s' refers to '%s', which is not an "
                        "instance of ForeignKey, and does not have a 'choices' definition." % (
                            label, field_name
                        ),
                        hint=None,
                        obj=cls,
                        id='admin.E023',
                    )
                ]
            else:
                return [] 

def generic_inlineformset_factory(model, form=ModelForm,
                                  formset=BaseGenericInlineFormSet,
                                  ct_field="content_type", fk_field="object_id",
                                  fields=None, exclude=None,
                                  extra=3, can_order=False, can_delete=True,
                                  max_num=None, formfield_callback=None,
                                  validate_max=False, for_concrete_model=True,
                                  min_num=None, validate_min=False):
    """
    Returns a ``GenericInlineFormSet`` for the given kwargs.

    You must provide ``ct_field`` and ``fk_field`` if they are different from
    the defaults ``content_type`` and ``object_id`` respectively.
    """
    opts = model._meta
    # if there is no field called `ct_field` let the exception propagate
    ct_field = opts.get_field(ct_field)
    if not isinstance(ct_field, models.ForeignKey) or ct_field.rel.to != ContentType:
        raise Exception("fk_name '%s' is not a ForeignKey to ContentType" % ct_field)
    fk_field = opts.get_field(fk_field)  # let the exception propagate
    if exclude is not None:
        exclude = list(exclude)
        exclude.extend([ct_field.name, fk_field.name])
    else:
        exclude = [ct_field.name, fk_field.name]
    FormSet = modelformset_factory(model, form=form,
                                   formfield_callback=formfield_callback,
                                   formset=formset,
                                   extra=extra, can_delete=can_delete, can_order=can_order,
                                   fields=fields, exclude=exclude, max_num=max_num,
                                   validate_max=validate_max, min_num=min_num,
                                   validate_min=validate_min)
    FormSet.ct_field = ct_field
    FormSet.ct_fk_field = fk_field
    FormSet.for_concrete_model = for_concrete_model
    return FormSet 

def forwards(self, orm):
        # Adding M2M table for field user_stars on 'Project'
        m2m_table_name = db.shorten_name(u'api_project_user_stars')
        db.create_table(m2m_table_name, (
            ('id', models.AutoField(verbose_name='ID', primary_key=True, auto_created=True)),
            ('project', models.ForeignKey(orm['api.project'], null=False)),
            ('user', models.ForeignKey(orm[u'auth.user'], null=False))
        ))
        db.create_unique(m2m_table_name, ['project_id', 'user_id']) 

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 sql_for_inline_many_to_many_references(self, model, field, style):
        opts = model._meta
        qn = self.connection.ops.quote_name

        columndef = '    {column} {type} {options},'
        table_output = [
            columndef.format(
                column=style.SQL_FIELD(qn(field.m2m_column_name())),
                type=style.SQL_COLTYPE(models.ForeignKey(model).db_type(
                    connection=self.connection)),
                options=style.SQL_KEYWORD('NOT NULL')
            ),
            columndef.format(
                column=style.SQL_FIELD(qn(field.m2m_reverse_name())),
                type=style.SQL_COLTYPE(models.ForeignKey(field.rel.to).db_type(
                    connection=self.connection)),
                options=style.SQL_KEYWORD('NOT NULL')
            ),
        ]

        deferred = [
            (field.m2m_db_table(), field.m2m_column_name(), opts.db_table,
                opts.pk.column),
            (field.m2m_db_table(), field.m2m_reverse_name(),
                field.rel.to._meta.db_table, field.rel.to._meta.pk.column)
        ]
        return table_output, deferred 

def __init__(self, to, on_delete=models.DO_NOTHING, related_name=None, related_query_name=None,
                 limit_choices_to=None, parent_link=False, to_field=None, db_constraint=False,  **kwargs):
        super(ForeignKey, self).__init__(to, on_delete, related_name, related_query_name, limit_choices_to,
                                         parent_link, to_field, db_constraint, **kwargs) 

def create_snapshot_model(cls, fields=[]):
    """ Dynamically create a main Model, 1-1 with the model being snapshotted. """
    # Models must have unique names, so we create a name by suffixing model class name with 'Snapshot'
    name = cls.__name__ + 'Snapshot'

    class Meta:
        db_table = '%s_snapshot' % cls._meta.db_table
        app_label = cls._meta.app_label
        verbose_name = u'%s - snapshot' % cls._meta.verbose_name
        verbose_name_plural = u'%s - snapshoty' % cls._meta.verbose_name
        ordering = ['-created_at']

    # Set up a dictionary to simulate declarations within a class.
    attrs = {
        '__module__': cls.__module__,
        'Meta': Meta,
        'id': models.AutoField(primary_key=True),
        'created_at': models.DateTimeField(u"stworzony dnia", auto_now_add=True),
        'snapshot_of': models.ForeignKey(cls, verbose_name=u"dotyczy", null=False, on_delete=models.PROTECT, related_name="snapshots"),
        '__unicode__': lambda self: u'snapshot',
    }

    # Copy fields
    for field_name in fields:
        target_field = cls._meta.get_field_by_name(field_name)[0]
        attrs[field_name] = copy_field(target_field)

    return type(name, (models.Model,), attrs) 

def test_foreignkey_type(self):
        """Test how the foreignkeys are rendered."""
        self.assertEqual(
            docstrings._get_field_type(SimpleModel._meta.get_field("user")),
            ":type user: ForeignKey to :class:`~django.contrib.auth.models.User`",
        )
        self.assertEqual(
            docstrings._get_field_type(SimpleModel._meta.get_field("user2")),
            ":type user2: ForeignKey to"
            " :class:`~sphinxcontrib_django.tests.test_docstrings.User2`",
        )
        self.assertEqual(
            docstrings._get_field_type(SimpleModel._meta.get_field("user3")),
            ":type user3: ForeignKey to :class:`~django.contrib.auth.models.User`",
        ) 

def setUp(self):
        self.time_func = TimeFormatFactory.get_time_func('string')
        # DATABASES = {
        #     'default': {
        #     'ENGINE': 'django.db.backends.sqlite3',
        #     'NAME': ':memory:',
        #     'USER': '',                      # Not used with sqlite3.
        #     'PASSWORD': '',                  # Not used with sqlite3.
        #     'HOST': '',                      # Set to empty string for localhost. Not used with sqlite3.
        #     'PORT': '',
        #     }
        # }
        # settings.configure(DATABASES=DATABASES, DEBUG=True)
        # class TestAuthor(models.Model):
        #     name = models.CharField(default='test_author')
        #
        #     def __unicode__(self):
        #         return self.name
        #
        # class TestTags(models.Model):
        #     tag = models.CharField(default='test_tag')
        #     create_time = models.DateTimeField(auto_now=True)
        #
        # class TestArticle(models.Model):
        #     title = models.CharField(default='test')
        #     content = models.CharField(default='test')
        #     author = models.ForeignKey(TestAuthor, related_name='author_art')
        #     tags = models.ManyToManyField(TestTags, related_name='tag_art')
        #     create_time = models.DateTimeField(auto_now=True)
        #
        #
        # self.author = TestAuthor()
        # self.author.save()
        # tags = TestTags(tag='tag1')
        # tags.save()
        # self.article = TestArticle(author=self.author)
        # self.article.tags.add(tags)
        # self.article.save() 

def deconstruct(self):
        name, path, args, kwargs = super().deconstruct()
        kwargs['on_delete'] = self.remote_field.on_delete
        kwargs['from_fields'] = self.from_fields
        kwargs['to_fields'] = self.to_fields

        if self.remote_field.parent_link:
            kwargs['parent_link'] = self.remote_field.parent_link
        # Work out string form of "to"
        if isinstance(self.remote_field.model, str):
            kwargs['to'] = self.remote_field.model
        else:
            kwargs['to'] = "%s.%s" % (
                self.remote_field.model._meta.app_label,
                self.remote_field.model._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 ForeignKey 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 validate_fk_name(self, cls, model):
        " Validate that fk_name refers to a ForeignKey. "
        if cls.fk_name:  # default value is None
            f = get_field(cls, model, 'fk_name', cls.fk_name)
            if not isinstance(f, models.ForeignKey):
                raise ImproperlyConfigured("'%s.fk_name is not an instance of "
                        "models.ForeignKey." % cls.__name__) 

def test_invalid_base_fields(self):
        class Related(models.Model):
            field = encrypt(
                models.ForeignKey('fields.EncryptedIntegerModel',
                                  models.CASCADE))

            class Meta:
                app_label = 'myapp'

        obj = Related()
        errors = obj.check()
        self.assertEqual(1, len(errors))
        self.assertEqual('encrypted.E002', errors[0].id) 

def tree_authorization(fields=None, tree_model='incidents.BusinessLine', owner_field=None, owner_permission=None):
    def set_meta(cls):
        if not hasattr(cls, '_authorization_meta'):
            class AuthorizationMeta:
                owner_field = None
                owner_permission = None
                fields = ('business_lines',)
                tree_model = None

                @property
                def model(self):
                    if isinstance(self.tree_model, six.string_types):
                        self.tree_model = apps.get_model(*self.tree_model.split('.'))
                    return self.tree_model

            AuthorizationMeta.tree_model = tree_model
            cls._authorization_meta = AuthorizationMeta()
        if fields is not None:
            if isinstance(fields, (tuple, list)):
                cls._authorization_meta.fields = fields
            elif isinstance(fields, six.string_types):
                cls._authorization_meta.fields = (fields,)
            else:
                raise Exception("Linking field unrecognized")
        for field in cls._authorization_meta.fields:
            f = cls._meta.get_field(field)
            if not isinstance(f, (models.ForeignKey, models.ManyToManyField)):
                raise Exception("Linking field not a link")
        if isinstance(owner_permission, six.string_types) and isinstance(owner_field, six.string_types):
            f = cls._meta.get_field(owner_field)
            if isinstance(f, models.ForeignKey):
                cls._authorization_meta.owner_permission = owner_permission
                cls._authorization_meta.owner_field = owner_field
        cls.get_authorization_filter = classmethod(get_authorization_filter)
        cls.add_to_class('has_perm', has_perm)
        cls.has_model_perm = classmethod(has_model_perm)
        AuthorizationManager().contribute_to_class(cls, 'authorization')
        return cls

    return set_meta 

def guess_field_formatters(self, faker):
        """
        Gets the formatter methods for each field using the guessers
        or related object fields
        :param faker: Faker factory object
        """
        formatters = {}
        name_guesser = NameGuesser(faker)
        field_type_guesser = FieldTypeGuesser(faker)

        for field in self.model._meta.fields:

            field_name = field.name

            if field.primary_key:
                continue

            if field.get_default():
                formatters[field_name] = field.get_default()
                continue

            if isinstance(field, (ForeignKey, ManyToManyField, OneToOneField)):
                formatters[field_name] = self.build_relation(field, field.related_model)
                continue

            if not field.choices:
                formatter = name_guesser.guess_format(field_name)
                if formatter:
                    formatters[field_name] = formatter
                    continue

            formatter = field_type_guesser.guess_format(field)
            if formatter:
                formatters[field_name] = formatter
                continue

        return formatters 

def _check_field_name(self):
        field_name = self._get_field_name()
        try:
            field = self.model._meta.get_field(field_name)
        except FieldDoesNotExist:
            return [
                checks.Error(
                    "CurrentSiteManager could not find a field named '%s'." % field_name,
                    hint=None,
                    obj=self,
                    id='sites.E001',
                )
            ]

        if not isinstance(field, (models.ForeignKey, models.ManyToManyField)):
            return [
                checks.Error(
                    "CurrentSiteManager cannot use '%s.%s' as it is not a ForeignKey or ManyToManyField." % (
                        self.model._meta.object_name, field_name
                    ),
                    hint=None,
                    obj=self,
                    id='sites.E002',
                )
            ]

        return [] 

def __init__(self, to, on_delete=models.DO_NOTHING, related_name=None, related_query_name=None,
                 limit_choices_to=None, parent_link=False, to_field=None, db_constraint=False,  **kwargs):
        super(ForeignKey, self).__init__(to, on_delete, related_name, related_query_name, limit_choices_to,
                                         parent_link, to_field, db_constraint, **kwargs)