docs: function (elem)
      {
          var impNode;
          var xmlGen = Strophe.xmlGenerator();
          try {
              impNode = (xmlGen.importNode !== undefined);
          }
          catch (e) {
              impNode = false;
          }
          var newElem = impNode ?
                        xmlGen.importNode(elem, true) :
                        Strophe.copyElement(elem);
          this.node.appendChild(newElem);
          this.node = newElem;
          return this;
      }