docs: public void renderExtendedTab(Collection<I_CmsFormField> fields, FlowPanel tab) {
  
          List<CmsFieldSet> result = new ArrayList<CmsFieldSet>();
  
          tab.clear();
  
          String used = Messages.get().key(Messages.GUI_PROPERTY_BLOCK_USED_0);
          CmsFieldSet usedFieldSet = new CmsFieldSet();
          usedFieldSet.addStyleName(I_CmsInputLayoutBundle.INSTANCE.inputCss().formGradientBackground());
          usedFieldSet.setLegend(used);
          usedFieldSet.setAnimationDuration(50);
  
          String unused = Messages.get().key(Messages.GUI_PROPERTY_BLOCK_UNUSED_0);
          CmsFieldSet unusedFieldSet = new CmsFieldSet();
          unusedFieldSet.addStyleName(I_CmsInputLayoutBundle.INSTANCE.inputCss().formGradientBackground());
          unusedFieldSet.setOpen(false);
          unusedFieldSet.setLegend(unused);
          unusedFieldSet.setAnimationDuration(50);
          boolean reopen = false;
          final String currentMarkedProperty = m_markedProperty;
          m_markedProperty = null;
          for (I_CmsFormField field : fields) {
              if (isTop(field)) {
                  usedFieldSet.addContent(createRow(field));
              } else {
                  if ((currentMarkedProperty != null)
                      && field.getLayoutData().get(LD_PROPERTY).equals(currentMarkedProperty)) {
                      reopen = true;
                  }
                  unusedFieldSet.addContent(createRow(field));
              }
          }
          if (reopen) {
              unusedFieldSet.setOpen(true);
          }
  
          if (usedFieldSet.getWidgetCount() > 0) {
              result.add(usedFieldSet);
          }
          if (unusedFieldSet.getWidgetCount() > 0) {
              result.add(unusedFieldSet);
          }
  
          Iterator<CmsFieldSet> iter = result.iterator();
          while (iter.hasNext()) {
              CmsFieldSet fieldSet = iter.next();
              if (iter.hasNext()) {
                  fieldSet.getElement().getStyle().setMarginTop(9, Unit.PX);
              } else {
                  fieldSet.getElement().getStyle().setMarginTop(15, Unit.PX);
              }
              tab.add(fieldSet);
          }
          CmsDomUtil.resizeAncestor(tab.getParent());
      }