def __set__(self, instance, value):
        if instance != None:
            raise AttributeError("Manager must be accessed via instance")

        manager = self.__get__(instance)
        # If the foreign key can support nulls, then completely clear the related set.
        # Otherwise, just move the named objects into the set.
        if self.related.field.null:
            manager.clear()
        manager.add(*value)
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/django/db/models/fields/related.py/ForeignRelatedObjectsDescriptor.__set__/operator `is` -> `!=`