@Override
  public List<Content> cloneContent() {
    int size = getContentSize();
    List<Content> list = new ArrayList<>(size);
    for (int i = 0; i < size; i++) {
      Content child = getContent(i);
      list.add(child.clone());
    }
    return list;
  }
@Override
  public List<Content> cloneContent()