code: func (err readError) Error() string {
  	switch err.Reason {
  	case ErrBlankSectionName:
  		return "empty section name not allowed"
  	case ErrCouldNotParse:
  		return fmt.Sprintf("could not parse line: %s", string(err.Content))
  	}
  	return "invalid read error"
  }
docs: // Error implement Error interface.