private static function createConfiguration(array $config, ContainerInterface $container = null)
    {
        $cache = $config['cache'];

        if ($container && is_string($config['cache']) && $container->has($config['cache'])) {
            $cache = $container->get($config['cache']);
        }

        return Setup::createConfiguration($config['debug'], $config['proxy_dir'], $cache);
    }