code: func (h *ArchiveHandler) Open(u *url.URL, mode int32) (File, error) {
  	switch mode {
  	case OpenModeReadOnly:
  		return h.newArchiveFromGuest(u)
  	case OpenModeWriteOnly:
  		return h.newArchiveToGuest(u)
  	default:
  		return nil, os.ErrNotExist
  	}
  }
docs: // Open implements FileHandler.Open