code: public function renderPage(PageInterface $page, $vars = array())
      {
          return $this->render(
              $this->getPageManager()->getTemplate($page),
              $vars + array(
                  'page' => $page,
                  'id' => $page->getId(),
              )
          );
      }
docs: Render a page with the specified additional template variables.
  
  @param PageInterface $page
  @param array $vars
  @return \Symfony\Component\HttpFoundation\Response