gistfile1.py

from django.db.models.fields.related import ReverseManyRelatedObjectsDescriptor
from django.db.models import ManyToManyField

class NewReverseManyRelatedObjectsDescriptor(ReverseManyRelatedObjectsDescriptor):

    def make_id_list(self, obj):

        through = self.field.rel.through
        name = self.field.m2m_field_name()
        related_name =self.field.m2m_reverse_field_name()

        def id_list():
            return through._default_manager.filter(**{name:obj.id}).values_list(related_name, flat=True)
        return id_list

    def __get__(self, instance, instance_type=None):
        manager = super(NewReverseManyRelatedObjectsDescriptor, self).__get__(instance, instance_type=None)
        new_func = self.make_id_list(instance)
        setattr(manager, "id_list", new_func)
        return manager

class NewManyToManyField(ManyToManyField):
    def contribute_to_class(self, cls, name):
        super(NewManyToManyField, self).contribute_to_class(cls, name)
        setattr(cls, self.name, NewReverseManyRelatedObjectsDescriptor(self))