docs: private void initSelectButtons() {
  
          m_selectGroup = new CmsTriStateCheckBox("");
          m_selectGroup.addStyleName(I_CmsInputLayoutBundle.INSTANCE.inputCss().inlineBlock());
          m_selectGroup.setNextStateAfterIntermediateState(State.on);
          m_selectGroup.addValueChangeHandler(new ValueChangeHandler<CmsTriStateCheckBox.State>() {
  
              public void onValueChange(ValueChangeEvent<State> event) {
  
                  State state = event.getValue();
                  if (state == State.on) {
                      m_model.signalGroup(Signal.publish, m_groupIndex);
                  } else if (state == State.off) {
                      m_model.signalGroup(Signal.unpublish, m_groupIndex);
                  }
              }
  
          });
          m_header.add(m_selectGroup);
      }