code: func Parse(s string) (UUID, error) {
  	s = strings.Replace(s, "-", "", -1)
  	b, err := hex.DecodeString(s)
  	if err != nil {
  		return nil, err
  	}
  	if err := lenErr(len(b)); err != nil {
  		return nil, err
  	}
  	return UUID(Reverse(b)), nil
  }
docs: // Parse parses a standard-format UUID string, such
  // as "1800" or "34DA3AD1-7110-41A1-B1EF-4430F509CDE7".