code: public function bootstrap($appBootstrap, $appenv, $debug)
      {
          $bootstrap = (new $appBootstrap());
          $bootstrap->initialize($appenv, $debug);
          $kernel = $bootstrap->getApplication();
          $this->requestHandler = new RequestHandler($kernel);
      }
docs: Bootstrap an application.
  
  @param string|null $appBootstrap
  @param string      $appenv
  @param bool        $debug