code: func (uuid UUID) Variant() Variant {
  	switch {
  	case (uuid[8] & 0xc0) == 0x80:
  		return RFC4122
  	case (uuid[8] & 0xe0) == 0xc0:
  		return Microsoft
  	case (uuid[8] & 0xe0) == 0xe0:
  		return Future
  	default:
  		return Reserved
  	}
  }
docs: // Variant returns the variant encoded in uuid.