/**
  * Geerate tags (such as stylesheet tags) that are required for the HEAD portion of the HTML output.
  *
  * @return string The HTML tags to go into the HEAD portion.
  */
 protected function get_head_contents()
 {
     $out = '';
     if (count($this->_stylesheets)) {
         $mod = \cge_utils::get_cge();
         foreach ($this->_stylesheets as $one) {
             if (!file_exists($one)) {
                 continue;
             }
             $url = \cge_utils::file_to_url($one);
             if (!$url) {
                 continue;
             }
             $out .= '<link rel="stylesheet" type="text/css" href="' . $url . '">';
         }
     }
     return $out;
 }