def parent_key(self):
    if self._parent_key is not None:
      return self._parent_key
    elif self._parent is not None:
      return self._parent.key()
    elif self._entity is not None:
      return self._entity.parent()
    elif self._key is not None:
      return self._key.parent()
    else:
      return None
Get the parent's key.
dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/ext/db/__init__.py/Model.parent_key