code: @SuppressWarnings("unchecked")
    public void addChildren(List<? extends N> children) {
      // NOTE: if the input list comes from another node, this could cause
      // ConcurrentModificationExceptions as nodes are moved from one parent to another.  To avoid
      // this we make a copy of the input list.
      for (Node child : children.toArray(new Node[0])) {
        addChild((N) child);
      }
    }
docs: Adds the given children.
  
  @param children The children to add.