code: public function getUrls()
      {
          if (is_integer($this->focus)) {
              return $this->frames[$this->focus]->getUrls();
          }
          $urls = array();
          foreach ($this->frames as $frame) {
              $urls = array_merge($urls, $frame->getUrls());
          }
  
          return array_values(array_unique($urls));
      }
docs: Accessor for a list of all fixed links.
  
  @return array   List of urls as strings.