public function parseXml($entryXml)
    {
        $this->_entry->parseXml($entryXml);
        $content = $this->_entry->getContent();
        if (is_null($content)) {
            $this->_subscriptionDescription = null;
        } else {
            $this->_subscriptionDescription = SubscriptionDescription::create(
                $content->getText()
            );
        }
    }