Contao\CoreBundle\Framework\ContaoFrameworkInterface::createInstance PHP Method

    public function createInstance($class, $args = []);

 /**
  * Renders an insert tag.
  *
  * @param string $insertTag
  *
  * @return Response
  */
 public function renderAction($insertTag)
 {
     $this->framework->initialize();
     /** @var InsertTags $it */
     $it = $this->framework->createInstance('Contao\\InsertTags');
     // Never cache these responses
     return (new Response($it->replace($insertTag, false)))->setPrivate();
 }