static boolean areElementsEqual(@Nullable Element e1, @Nullable Element e2) {
    if (e1 == null && e2 == null) return true;
    if (e1 == null || e2 == null) return false;

    return Objects.equals(e1.getName(), e2.getName())
           && isAttributesEqual(e1.getAttributes(), e2.getAttributes())
           && contentListsEqual(e1.getContent(CONTENT_FILTER), e2.getContent(CONTENT_FILTER));
  }
static boolean areElementsEqual(@Nullable Element e1, @Nullable Element e2)