code: public void doFetchRows (int start, int count, AsyncCallback<List<T>> callback)
      {
          List<T> subList = new ArrayList<T>();
          int limit = Math.min(count, _items.size()-start);
          for (int ii = 0; ii < limit; ii ++) {
              subList.add(_items.get(start + ii));
          }
          callback.onSuccess(subList);
      }
docs: from DataModel