code: protected function getContainerInitializer()
      {
          $initializer = new DefaultInitializer($this->getConfigurationProvider());
          if ($this->cache) {
              $initializer = new CachedInitializer($initializer, $this->getCacheDir());
          }
  
          return $initializer;
      }
docs: Returns a ContainerInitializer.
  
  A ContainerInitializer creates fully-built, ready-to-use containers.
  
  @return ContainerInitializerInterface