code: function(maxLevel) {
        var ul = this.el.childNodes[0];
        var liEls = ul.childNodes;
        for(var i = 0 ; i < liEls.length ; i++) {
           var li = liEls[i];
           this.expandBranch(li,maxLevel);
        }
     }
docs: Expand the root node
  @param {Integer} maxLevel