code: func PickStdFormat(w io.Writer) string {
  	if file, _ := w.(*os.File); file != nil {
  		if terminal.IsTerminal(int(file.Fd())) {
  			return StdFormatWithColor
  		}
  	}
  	return StdFormat
  }
docs: // PickStdFormat returns StdFormat for non terminal-backed files or
  // StdFormatWithColor for io.Writers that are io.Files backed by a terminal.
  //
  // Used by default StdConfig.