code: protected RadioGroup<T> newRadioGroup(final String id, final IModel<T> model)
  	{
  		final RadioGroup<T> group = ComponentFactory.newRadioGroup(id, model);
  		group.add(new AjaxFormChoiceComponentUpdatingBehavior()
  		{
  			private static final long serialVersionUID = 1L;
  
  			@Override
  			protected void onUpdate(final AjaxRequestTarget target)
  			{
  				RadioGroupPanel.this.onUpdate(target);
  			}
  		});
  		return group;
  	}
docs: Factory method for create the new {@link RadioGroup}. This method is invoked in the
  constructor from the derived classes and can be overridden so users can provide their own
  version of a new {@link RadioGroup}.
  
  @param id
  the id
  @param model
  the model
  @return the new {@link RadioGroup}