code: function() {
          var html = this.root.getHtml(),
              el = this.getEl();
          el.innerHTML = html;
          if (!this._hasEvents) {
              Event.on(el, 'click', this._onClickEvent, this, true);
              Event.on(el, 'dblclick', this._onDblClickEvent, this, true);
              Event.on(el, 'mouseover', this._onMouseOverEvent, this, true);
              Event.on(el, 'mouseout', this._onMouseOutEvent, this, true);
              Event.on(el, 'keydown', this._onKeyDownEvent, this, true);
          }
          this._hasEvents = true;
      }
docs: Renders the tree boilerplate and visible nodes
  @method render