code: func (l *Handler) Download(ctx context.Context, sessionID session.ID, writer io.WriterAt) error {
  	written, err := l.downloader.DownloadWithContext(ctx, writer, &s3.GetObjectInput{
  		Bucket: aws.String(l.Bucket),
  		Key:    aws.String(l.path(sessionID)),
  	})
  	if err != nil {
  		return ConvertS3Error(err)
  	}
  	if written == 0 {
  		return trace.NotFound("recording for %v is not found", sessionID)
  	}
  	return nil
  }
docs: // Download downloads recorded session from S3 bucket and writes the results into writer
  // return trace.NotFound error is object is not found