code: function() {
          // Since the label editor can be separated from the main TreeView control
          // the destroy method for it might not be there.
          if (this._destroyEditor) { this._destroyEditor(); }
          var el = this.getEl();
          Event.removeListener(el,'click');
          Event.removeListener(el,'dblclick');
          Event.removeListener(el,'mouseover');
          Event.removeListener(el,'mouseout');
          Event.removeListener(el,'keydown');
          for (var i = 0 ; i < this._nodes.length; i++) {
              var node = this._nodes[i];
              if (node && node.destroy) {node.destroy(); }
          }
          el.innerHTML = '';
          this._hasEvents = false;
      }
docs: Nulls out the entire TreeView instance and related objects, removes attached
  event listeners, and clears out DOM elements inside the container. After
  calling this method, the instance reference should be expliclitly nulled by
  implementer, as in myDataTable = null. Use with caution!
  
  @method destroy