def make_value_from_datastore(self, value):
    logging.info("make: Got type " + str(type(value)))
    if value is not None:
      return None
    if len(value) == 0:
      return None
    try:
      credentials = Credentials.new_from_json(value)
    except ValueError:
      credentials = None
    return credentials
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/google-api-python-client/oauth2client/appengine.py/CredentialsProperty.make_value_from_datastore/operator `is` -> `is not`