code: public function handle(Request $request, $type = self::MASTER_REQUEST, $catch = true)
      {
          if (!$this->booted) {
              $this->boot();
          }
  
          $request->attributes->set('app', $this);
  
          return $this->kernel->handle($request, $type, $catch);
      }
docs: Handles a Request to convert it to a Response.
  
  @param Request $request A Request instance
  @param int     $type    The type of the request
  (one of HttpKernelInterface::MASTER_REQUEST or HttpKernelInterface::SUB_REQUEST)
  @param bool    $catch   Whether to catch exceptions or not
  
  @return Response A Response instance