code: private void addModelGroupSettings(
          CmsContainerElementData elementBean,
          CmsContainerPageElementPanel elementWidget,
          CmsFieldSet fieldSet) {
  
          Map<String, String> groupOptions = new LinkedHashMap<String, String>();
          groupOptions.put(GroupOption.disabled.name(), GroupOption.disabled.getLabel());
          groupOptions.put(GroupOption.copy.name(), GroupOption.copy.getLabel());
          groupOptions.put(GroupOption.reuse.name(), GroupOption.reuse.getLabel());
          m_modelGroupSelect = new CmsSelectBox(groupOptions);
          if (elementWidget.isModelGroup()) {
              if (Boolean.valueOf(elementBean.getSettings().get(CmsContainerElement.USE_AS_COPY_MODEL)).booleanValue()) {
                  m_modelGroupSelect.selectValue(GroupOption.copy.name());
              } else {
                  m_modelGroupSelect.selectValue(GroupOption.reuse.name());
              }
          }
          CmsFormRow selectRow = new CmsFormRow();
          selectRow.getLabel().setText(Messages.get().key(Messages.GUI_USE_AS_MODEL_GROUP_LABEL_0));
          selectRow.getWidgetContainer().add(m_modelGroupSelect);
          fieldSet.add(selectRow);
      }
docs: Adds the model group settings fields to the given field set.<p>
  
  @param elementBean the element bean
  @param elementWidget the element widget
  @param fieldSet the field set