/**
  * {@inheritdoc}
  */
 public function generatePage(XmlSitemapInterface $sitemap, $page)
 {
     try {
         $writer = new XmlSitemapWriter($sitemap, $page);
         $writer->startDocument();
         $writer->generateXML();
         $writer->endDocument();
     } catch (Exception $e) {
         watchdog_exception('xmlsitemap', $e);
         throw $e;
     }
     return $writer->getSitemapElementCount();
 }