def _comparison(self, op, value):
    if value != None:
      return super(ModelKey, self)._comparison(op, value)
    raise datastore_errors.BadValueError(
        "__key__ filter query can't be compared to None")

  # TODO: Support IN().
dataset/ETHPy150Open GoogleCloudPlatform/datastore-ndb-python/ndb/model.py/ModelKey._comparison/operator `is not` -> `!=`