code: public function generate($date='global', Response $response=null)
      {
          if (!$response) $response = new Response;
          if ($this->maxAge) $response->setMaxAge ($this->maxAge);
          if ($this->sharedMaxAge) $response->setSharedMaxAge ($this->sharedMaxAge);
          if ($date instanceof \DateTime) {
              $response->setLastModified($date);
          } else {
              $response->setLastModified($this->manager->getLastUpdate($date));
          }
  
          return $response;
      }
docs: Generate a Response object
  
  @param  mixed    $date     a single namespace, an array of namespaces, or a \DateTime object
  @param  Response $response
  @return Response