public void readExternal(@NotNull Element element)  {
    List<Element> subPanes = element.getChildren(ELEMENT_SUB_PANE);
    for (Element subPane : subPanes) {
      String subId = subPane.getAttributeValue(ATTRIBUTE_SUB_ID);
      TreeState treeState = TreeState.createFrom(subPane);
      if (!treeState.isEmpty()) {
        myReadTreeState.put(subId, treeState);
      }
    }
  }
public void readExternal(@NotNull Element element)