class ItemGroup extends AbstractItemHierarchy implements ItemInflater.ItemParent,
        ItemHierarchy.Observer {

    public void clear() {
        if (mChildren.size() == 0) {
            return;
        }

        final int numRemoved = getCount();

        for (ItemHierarchy item : mChildren) {
            item.unregisterObserver(this);
        }
        mDirty = true;
        mChildren.clear();
        notifyItemRangeRemoved(0, numRemoved);
    }

    public  ItemGroup();
    public  ItemGroup(Context context, AttributeSet attrs);

}