code: public function commit()
      {
          foreach ($this->deferred as $item) {
              /* @var $item \Psr6NullCache\CacheItem */
              $this->save($item);
          }
          
          $this->deferred = [];
          
          return true;
      }
docs: Persists any deferred cache items.
  
  @return bool True if all not-yet-saved items were successfully saved or there were none. False otherwise.