def value_from_object(self, obj):
		qs = super(ForeignKeyAttribute, self).value_from_object(obj)
		try:
			return qs.values_list('pk', flat=True)
		except:
			return []
Converts the default value type (a queryset) to a list of pks.
dataset/ETHPy150Open ithinksw/philo/philo/models/fields/entities.py/ManyToManyAttribute.value_from_object