code: public function insert($strName, array $arrData = null)
      {
          if (TL_MODE == 'BE') {
              $objTemplate = new \BackendTemplate($strName);
          } else {
              $objTemplate = new \FrontendTemplate($strName);
          }
  
          if ($arrData !== null) {
              $objTemplate->setData($arrData);
          }
  
          echo $objTemplate->parse($this->getFormat());
      }
docs: Insert a template
  
  @param string $strName The template name.
  @param array  $arrData An optional data array.
  
  @return void