public function getSessionKey(): ?string
    {
        $cacheKey = 'sessionkey';
        if (!isset(self::$cache[$cacheKey])) {
            $cookies = Internal\Cookies::getList(Internal\Cookies::TYPE_SERVER);
            $cookieKey = '_s';
            $key = isset($cookies[$cookieKey]) ? (string) $cookies[$cookieKey] : '';
            self::$cache[$cacheKey] = strlen((string) $key) > 70 ? $key : null;
        }
        return self::$cache[$cacheKey];
    }