code: protected CheckGroup<T> newCheckGroup(final String id,
  		final IModel<? extends Collection<T>> model)
  	{
  		final CheckGroup<T> checkGroup = ComponentFactory.newCheckGroup(id, model);
  		checkGroup.add(new AjaxFormChoiceComponentUpdatingBehavior()
  		{
  			/** The serialVersionUID. */
  			private static final long serialVersionUID = 1L;
  
  			/**
  			 * {@inheritDoc}
  			 */
  			@Override
  			protected void onUpdate(final AjaxRequestTarget target)
  			{
  				CheckGroupSelectorPanel.this.onUpdate(target);
  			}
  		});
  		return checkGroup;
  	}
docs: Factory method for create a new {@link CheckGroup}. 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 CheckGroup}.
  
  @param id
  the id
  @param model
  the model
  @return the new {@link CheckGroup}