code: public void insertItem (T item, int index, String label)
      {
          insertItem(label == null ? toLabel(item) : label, index);
          _items.add(index, item);
      }
docs: Inserts the supplied item into this list box at the specified position, using the specified
  label if given. If no label is given, {@link #toLabel(Object)} is used to calculate it.