code: function ($node) {
        var that = this;
        var $levels = $node.closest('tr').siblings();
        var isVerticalDesc = $levels.is('.verticalNodes') ? true : false;
        var $animatedNodes = isVerticalDesc
          ? $levels.removeClass('hidden').find('.node').filter(this.isVisibleNode.bind(this))
          : $levels.removeClass('hidden').eq(2).children().find('.node:first').filter(this.isVisibleNode.bind(this));
        // the two following statements are used to enforce browser to repaint
        this.repaint($animatedNodes.get(0));
        $animatedNodes.addClass('sliding').removeClass('slide-up').eq(0).one('transitionend', { 'node': $node, 'animatedNodes': $animatedNodes }, this.showChildrenEnd.bind(this));
      }
docs: show the children nodes of the specified node