code: func IsTransientAPIError(err error) bool {
  	if err == nil {
  		return false
  	}
  	apiErr, _ := err.(*googleapi.Error)
  	if apiErr == nil {
  		return true // failed to get HTTP code => connectivity error => transient
  	}
  	return apiErr.Code >= 500 || apiErr.Code == 429 || apiErr.Code == 0
  }
docs: // IsTransientAPIError returns true if error from Google API client indicates
  // an error that can go away on its own in the future.