code: func (w *writer) Cancel() error {
  	w.closed = true
  	err := storageDeleteObject(cloud.NewContext(dummyProjectID, w.client), w.bucket, w.name)
  	if err != nil {
  		if status, ok := err.(*googleapi.Error); ok {
  			if status.Code == http.StatusNotFound {
  				err = nil
  			}
  		}
  	}
  	return err
  }
docs: // Cancel removes any written content from this FileWriter.