@SuppressWarnings("deprecation")
  public static void addChildren(@NotNull Element parent,
                                 @NotNull String childElementName,
                                 @NotNull Collection<? extends JDOMExternalizable> children) throws WriteExternalException {
    for (JDOMExternalizable child : children) {
      if (child != null) {
        Element element = new Element(childElementName);
        child.writeExternal(element);
        parent.addContent(element);
      }
    }
  }
@SuppressWarnings("deprecation")
  public static void addChildren(@NotNull Element parent,
                                 @NotNull String childElementName,
                                 @NotNull Collection<? extends JDOMExternalizable> children)