code: func (s *TranslateFile) Reader(ctx context.Context, offset int64) (io.ReadCloser, error) {
  	rc := newTranslateFileReader(ctx, s, offset)
  	if err := rc.Open(); err != nil {
  		return nil, err
  	}
  	return rc, nil
  }
docs: // Reader returns a reader that streams the underlying data file.