code: func Decode(input string) ([]byte, error) {
  	if len(input) == 0 {
  		return nil, ErrEmptyString
  	}
  	if !has0xPrefix(input) {
  		return nil, ErrMissingPrefix
  	}
  	b, err := hex.DecodeString(input[2:])
  	if err != nil {
  		err = mapError(err)
  	}
  	return b, err
  }
docs: // Decode decodes a hex string with 0x prefix.