code: func IsUnprocessableEntityError(err error) bool {
  	if e, ok := err.(interface {
  		UnprocessableEntityError() bool
  	}); ok {
  		return e.UnprocessableEntityError()
  	}
  	if parent := parentOf(err); parent != nil {
  		return IsUnprocessableEntityError(parent)
  	}
  	return false
  }
docs: // IsDownloadDeclinedError indicates that the upload operation failed because of
  // an HTTP 422 response code.