code: public function generateClearAll($strContent, $strTemplate)
      {
          if (substr($strTemplate, 0, 3) === 'fe_') {
              if (preg_match_all(
                  '#\[\[\[metamodelfrontendfilterclearall::(ce|mod)::([^\]]*)\]\]\]#',
                  $strContent,
                  $arrMatches,
                  PREG_SET_ORDER
              )) {
                  foreach ($arrMatches as $arrMatch) {
                      switch ($arrMatch[1]) {
                          case 'ce':
                              $strContent = $this->generateContentElement($strContent, $arrMatch[0], $arrMatch[2]);
                              break;
  
                          case 'mod':
                              $strContent = $this->generateModule($strContent, $arrMatch[0], $arrMatch[2]);
                              break;
  
                          default:
                              throw new \RuntimeException('Unexpected element determinator encountered: ' . $arrMatch[1]);
                      }
                  }
              }
          }
  
          return $strContent;
      }
docs: Add the "clear all Filter".
  
  This is called via parseTemplate HOOK to inject the "clear all" filter into fe_page.
  
  @param string $strContent  The whole page content.
  
  @param string $strTemplate The name of the template being parsed.
  
  @return string
  
  @throws \RuntimeException When an invalid selector has been used (different than "ce" or "mod").