docs: def WaitUntilValid(self, timeout=None):
      """Wait until the approval is valid (i.e. - approved).
  
      Args:
        timeout: timeout in seconds. None means default timeout (1 hour).
                 0 means no timeout (wait forever).
      Returns:
        Operation object with refreshed target_file.
      Raises:
        PollTimeoutError: if timeout is reached.
      """
  
      return utils.Poll(
          generator=self.Get,
          condition=lambda f: f.data.is_valid,
          timeout=timeout)