public static function keepRedirectUrls(PHPCrawlerDocumentInfo $DocumentInfo, $decrease_link_depths = false)
  {
    $cnt = count($DocumentInfo->links_found_url_descriptors);
    for ($x=0; $x<$cnt; $x++)
    {
      if ($DocumentInfo->links_found_url_descriptors[$x]->is_redirect_url == false)
      {
        $DocumentInfo->links_found_url_descriptors[$x] = null;
      }
      else if ($decrease_link_depths = true) // Decrease linkdepths
      {
        $DocumentInfo->links_found_url_descriptors[$x]->url_link_depth--;
      }
    }
  }