code: function(node) {
      var doc = '';
      var sibling = node.firstChild;
      var serializer = new XMLSerializer();
  
      while (sibling) {
        if (this.isElementNode(sibling)) {
          doc += serializer.serializeToString(sibling);
        }
        sibling = sibling.nextSibling;
      }
  
      return doc !== '' ? doc : null;
    }
docs: Given a dom node serializes all immediate children that are xml elements.
  @static
  @memberOf XmlUtil
  @param  {object} node  An xml dom node.
  @return {string}       Serialized xml.