  void sweep() FOLLY_OVERRIDE {
    // if m_domNode isn't null, then he owns the m_doc. Otherwise, I own it
    if (m_doc && m_domNode.isNull()) {
      xmlFreeDoc(m_doc);
    }
  }
  void sweep() FOLLY_OVERRIDE {
     
    if (m_doc && m_domNode.isNull()) {
      xmlFreeDoc(m_doc);
    }
  }