public AdvancedSearchPanel(String id, IModel<SearchControlsBase> model) {
    super(id, model);
    searchControlsBase = model.getObject();
    add(new CssClass("advanced-search-panel"));

    List<String> repoList = getOrderdRepoKeys();
    ListMultipleChoice choice = new ListMultipleChoice<String>("selectedRepoForSearch", repoList);
    choice.setOutputMarkupId(true);
    add(choice);

    collapsibleBehavior = new CollapsibleBehavior().setResizeModal(true).setUseAjax(true);
    add(collapsibleBehavior);
  }