def get_super_entities(self, model_objs, sync_all):
return {}<EOL>
Retrieves a dictionary of entity relationships. The dictionary is keyed
on the model class of the super entity and each value of the dictionary
is a list of tuples. The tuples specify the ID of the sub entity and
the ID of the super entity.

If sync_all is True, it means all models are currently being synced