code: public static <A extends FastItemAdapter<Item>, Item extends IItem> DiffUtil.DiffResult calculateDiff(final A adapter, final List<Item> items, final DiffCallback<Item> callback) {
          return calculateDiff(adapter.getItemAdapter(), items, callback);
      }
docs: convenient function for {@link #calculateDiff(ModelAdapter, List, DiffCallback, boolean)}
  
  @return the {@link androidx.recyclerview.widget.DiffUtil.DiffResult} computed.