docs: public void addChildren(
          CmsTreeItem parent,
          List<CmsCategoryTreeEntry> children,
          Collection<String> selectedCategories) {
  
          if (children != null) {
              for (CmsCategoryTreeEntry child : children) {
                  // set the category tree item and add to parent tree item
                  CmsTreeItem treeItem = buildTreeItem(child, selectedCategories);
                  m_childrens.get(parent.getId()).add(treeItem.getId());
                  m_childrens.put(treeItem.getId(), new ArrayList<>(child.getChildren().size()));
                  if ((selectedCategories != null) && selectedCategories.contains(child.getPath())) {
                      openWithParents(parent);
  
                  }
                  if (m_isSingleSelection) {
                      if (treeItem.getCheckBox().isChecked()) {
                          parent.getCheckBox().setChecked(false);
                      }
                  }
                  parent.addChild(treeItem);
                  addChildren(treeItem, child.getChildren(), selectedCategories);
              }
          }
      }