code: protected function loadFrame($frames, $url, $parameters)
      {
          $page = $this->fetch($url, $parameters);
          $this->page->setFrame($frames, $page);
  
          return $page->getRaw();
      }
docs: Fetches a frame into the existing frameset replacing the original.
  
  @param array $frames                    List of names to drill down.
  @param string/SimpleUrl $url            Target to fetch as string.
  @param SimpleFormEncoding $parameters   POST parameters.
  
  @return string                          Raw content of page.