code: func (l *Handler) Download(ctx context.Context, sessionID session.ID, writer io.WriterAt) error {
  	path := l.path(sessionID)
  	_, err := os.Stat(filepath.Dir(path))
  	f, err := os.Open(path)
  	if err != nil {
  		return trace.ConvertSystemError(err)
  	}
  	defer f.Close()
  	_, err = io.Copy(writer.(io.Writer), f)
  	if err != nil {
  		return trace.Wrap(err)
  	}
  	return nil
  }
docs: // Download downloads session recording from storage, in case of file handler reads the
  // file from local directory