code: func ParseHexStr(s string) (string, error) {
  	var err error
  	s, err = uniformHexStrLit(s)
  	if err != nil {
  		return "", errors.Trace(err)
  	}
  	bs, err := hex.DecodeString(s[2:])
  	if err != nil {
  		return "", errors.Trace(err)
  	}
  	return string(bs), nil
  }
docs: // ParseHexStr parses hexadecimal literal as string.
  // See https://dev.mysql.com/doc/refman/5.7/en/hexadecimal-literals.html