public function clearCache($handler_id = null, $store_id = null)
    {
        $pattern = 'ga_report.';

        if (isset($handler_id)) {
            $pattern .= "$handler_id.";
        }

        if (isset($store_id)) {
            $pattern .= "$store_id";
        }

        $this->cache->clear('', array('pattern' => "$pattern*"));
    }