code: function(view, childView, options) {
      var buffer = view.buffer;
  
      childView = this.createChildView(childView, options);
      view._childViews.push(childView);
  
      childView.renderToBuffer(buffer);
  
      view.propertyDidChange('childViews');
  
      return childView;
    }
docs: when a view is rendered in a buffer, appending a child view will render that view and append the resulting buffer into its buffer.