public static function sep()
    {
        if (static::$sep !== null) {
            return static::$sep;
        }

        if (defined('PHP_EOL')) {
            static::$sep = PHP_EOL;
        } else {
            static::$sep = (strpos(PHP_OS, 'WIN') === false) ? '\n' : '\r\n';
        }

        return static::$sep;
    }