protected function getCacheKey(array $assets)
    {
        $cacheKey = $this->localPath . implode('|', $assets);

        /*
         * Deep hashing
         */
        if ($this->useDeepHashing) {
            $cacheKey .= $this->getDeepHashFromAssets($assets);
        }

        /*
         * Extensibility
         */
        $dataHolder = (object) ['key' => $cacheKey];
        Event::fire('cms.combiner.getCacheKey', [$this, $dataHolder]);
        $cacheKey = $dataHolder->key;

        return md5($cacheKey);
    }