/**
  * Render COPage
  * 
  * @see ilContainerGUI
  * @return string
  */
 protected function getPageHTML()
 {
     global $tpl, $ilSetting, $ilUser;
     if (!$ilSetting->get("enable_cat_page_edit")) {
         return;
     }
     $page_id = $this->start_object->getObjId();
     // if page does not exist, return nothing
     include_once "./Services/COPage/classes/class.ilPageUtil.php";
     if (!ilPageUtil::_existsAndNotEmpty("cstr", $page_id)) {
         return;
     }
     include_once "./Services/Style/classes/class.ilObjStyleSheet.php";
     $tpl->setVariable("LOCATION_CONTENT_STYLESHEET", ilObjStyleSheet::getContentStylePath(0));
     $tpl->setCurrentBlock("SyntaxStyle");
     $tpl->setVariable("LOCATION_SYNTAX_STYLESHEET", ilObjStyleSheet::getSyntaxStylePath());
     $tpl->parseCurrentBlock();
     include_once "./Services/Container/classes/class.ilContainerStartObjectsPageGUI.php";
     $page_gui = new ilContainerStartObjectsPageGUI($page_id);
     include_once "./Services/Style/classes/class.ilObjStyleSheet.php";
     $page_gui->setStyleId(ilObjStyleSheet::getEffectiveContentStyleId(0));
     $page_gui->setPresentationTitle("");
     $page_gui->setTemplateOutput(false);
     $page_gui->setHeader("");
     return $page_gui->showPage();
 }