Add each of the names and fields in the ``fields`` attribute
        to the model the relationship field is applied to, and set up
        the related item save and delete signals for calling
        ``related_items_changed``.

def contribute_to_class(self, cls, name):
        """
        Add each of the names and fields in the ``fields`` attribute
        to the model the relationship field is applied to, and set up
        the related item save and delete signals for calling
        ``related_items_changed``.
        """
        for field in cls._meta.many_to_many:
            if isinstance(field, self.__class__):
                e = "Multiple %s fields are not supported (%s.%s, %s.%s)" % (
                    self.__class__.__name__, cls.__name__, cls.__name__,
                    name, field.name)
                raise ImproperlyConfigured(e)
        self.related_field_name = name
        super(BaseGenericRelation, self).contribute_to_class(cls, name)
        # Not applicable to abstract classes, and in fact will break.
        if not cls._meta.abstract:
            for (name_string, field) in self.fields.items():
                if "%s" in name_string:
                    name_string = name_string % name
                extant_fields = cls._meta._forward_fields_map
                if name_string in extant_fields:
                    continue
                if field.verbose_name is None:
                    field.verbose_name = self.verbose_name
                cls.add_to_class(name_string, copy(field))
            # Add a getter function to the model we can use to retrieve
            # the field/manager by name.
            getter_name = "get_%s_name" % self.__class__.__name__.lower()
            cls.add_to_class(getter_name, lambda self: name)

            sender = self.rel.to
            post_save.connect(self._related_items_changed, sender=sender)
            post_delete.connect(self._related_items_changed, sender=sender)