code: func (s *Stream) WriteSysEx(when Timestamp, msg string) error {
  	buf, err := hex.DecodeString(strings.Replace(msg, " ", "", -1))
  	if err != nil {
  		return err
  	}
  
  	return s.WriteSysExBytes(when, buf)
  }
docs: // WriteSysEx writes a system exclusive MIDI message given as a string of hexadecimal characters to
  // the output stream. The string must only consist of hex digits (0-9A-F) and optional spaces. This
  // function is case-insenstive.