private void computeModel() {
groupModels = new ArrayList<OptionGroupModel>();
for (Entity entity : entityList) {
List<OptionModel> options = new ArrayList<OptionModel>();
options.add(new OptionModelImpl(entity.getLabel(), entity));
OptionGroupModel groupModel = new OptionGroupModelImpl(entity.getLabel(), false, options);
groupModels.add(groupModel);
}