code: function(nodes, controller) {
          var that = this;
          this.show(nodes);
          this.animation.setOptions($.merge(controller, {
              $animating: false,
              compute: function(delta) {
                  that.plotStep(delta, controller, this.$animating);
                  this.$animating = 'expand';
              },
              
              complete: function() {
                  that.plotStep(undefined, controller, false);
                  controller.onComplete();
              }       
          })).start();
          
      }
docs: /*
  Expands group of nodes.