protected function getCacheImpl(CacheConfigurationInterface $cacheConfiguration)
    {

        // load the factory class
        $factory = $cacheConfiguration->getFactory();

        // create a cache instance
        $cache = $factory::get($cacheConfiguration->getParams());
        $cache->setNamespace(sprintf('dc2_%s_', md5($this->getPersistenceUnitNode()->getName())));

        // return the cache instance
        return $cache;
    }