private function isAdvanced(PageInterface $page)
    {
        if (null !== $controller = $page->getController()) {
            if (array_key_exists($controller, $this->pageConfig['controllers'])) {
                return $this->pageConfig['controllers'][$controller]['advanced'];
            }
            throw new \RuntimeException("Undefined page controller '{$controller}'.");
        }

        return null;
    }