docs: protected void doNotifyListenersOfAddedValues(int startIndex, List<R> newItems) {
          List<ListValueChangeListener<R>> listenersCopy = new ArrayList<ListValueChangeListener<R>>(listeners);
          List<R> unmodifiable = Collections.unmodifiableList(newItems);
          for (ListValueChangeListener<R> listener : listenersCopy) {
              listener.valuesAdded(this, startIndex, unmodifiable);
          }
      }