code: func ParseHex(s string) (Hex, error) {
  	var err error
  	s, err = uniformHexStrLit(s)
  	if err != nil {
  		return Hex{}, errors.Trace(err)
  	}
  	n, err := strconv.ParseInt(s, 0, 64)
  	if err != nil {
  		return Hex{}, errors.Trace(err)
  	}
  
  	return Hex{Value: n}, nil
  }
docs: // ParseHex parses hexadecimal literal string.
  // The string format can be X'val', x'val' or 0xval.
  // val must in (0...9, a...f, A...F).