code: private function warmUpSymfonyCache(): void
      {
          $cacheDir = $this->getContainerParameter('kernel.cache_dir');
  
          if (file_exists($cacheDir.'/contao/config/config.php')) {
              return;
          }
  
          $warmer = $this->container->get('cache_warmer');
  
          if (!$this->getContainerParameter('kernel.debug')) {
              $warmer->enableOptionalWarmers();
          }
  
          $warmer->warmUp($cacheDir);
  
          if (\function_exists('opcache_reset')) {
              opcache_reset();
          }
  
          if (\function_exists('apc_clear_cache') && !ini_get('apc.stat')) {
              apc_clear_cache();
          }
      }
docs: The method runs the optional cache warmers, because the cache will only
  have the non-optional stuff at this time.