code: def key_for_entity_group(cls, key):
      
      return model.Key(cls.KIND_NAME, cls.ID, parent=key.root())
docs: Return the key for the entity group containing key.
  
      Args:
        key: a key for an entity group whose __entity_group__ key you want.
  
      Returns:
        The __entity_group__ key for the entity group containing key.