public static function isValidCode($code)
    {
        if (array_key_exists($code, self::getInfoForCurrencies())) {
            return true;
        } elseif (array_key_exists($code, self::getInfoForCurrenciesWithoutCurrencyCode())) {
            return true;
        } elseif (array_key_exists($code, self::getInfoForCurrenciesWithUnofficialCode())) {
            return true;
        } elseif (array_key_exists($code, self::getInfoForCurrenciesWithHistoricalCode())) {
            return true;
        } else {
            return false;
        }
    }