public static function currencySymbol($code = null)
    {
        $localeCode = \Locale::getDefault();
        if ($code !== null) {
            $localeCode .= '@currency=' . $code;
        }
        $formatter = new \NumberFormatter($localeCode, \NumberFormatter::CURRENCY);
        $symbol = $formatter->getSymbol(\NumberFormatter::CURRENCY_SYMBOL);
        return $symbol != $code
            ? $symbol
            : (static::countryCurrencySymbol(substr($code, 0, 2))
                ?: $symbol);
    }