/**
  * {@inheritdoc}
  */
 public function listAttribute($content)
 {
     $this->crawler->addContent($content);
     $this->links = array();
     $this->crawler->filter('a')->each(function (HtmlPageCrawler $anchor, $uri) {
         $href = $anchor->attr('href');
         // @todo deprecated method.
         $this->links[] = $this->urlGenerator->generateFromPath($href, array('absolute' => TRUE));
     });
     $this->crawler->remove();
     return implode(',', $this->links);
 }