AssetManager\Service\AssetViewHelperFactory::loadCache PHP Method

    private function loadCache($serviceLocator, $config)
    {
        // check if the cache is configured
        if (!isset($config['view_helper']['cache']) || $config['view_helper']['cache'] === null) {
            return null;
        }
        // get the cache, if it's a string, search it among services
        $cache = $config['view_helper']['cache'];
        if (is_string($cache)) {
            $cache = $serviceLocator->get($cache);
        }
        // exception in case cache is not an Adapter that extend the AbstractAdapter of Zend\Cache\Storage
        if ($cache !== null && !$cache instanceof AbstractCacheAdapter) {
            throw new InvalidArgumentException('Invalid cache provided, you must pass a Cache Adapter that extend 
                Zend\\Cache\\Storage\\Adapter\\AbstractAdapter');
        }
        return $cache;
    }