code: def locked_get(self):
          
          credentials = None
          content = keyring.get_password(self._service_name, self._user_name)
  
          if content is not None:
              try:
                  credentials = client.Credentials.new_from_json(content)
                  credentials.set_store(self)
              except ValueError:
                  pass
  
          return credentials
docs: Retrieve Credential from file.
  
          Returns:
              oauth2client.client.Credentials