code: public void addItem(T value, String text, boolean reload) {
          values.add(value);
          listBox.addItem(text, keyFactory.generateKey(value));
  
          if (reload) {
              reload();
          }
      }
docs: Adds an item to the list box, specifying an initial value for the item.
  
  @param value  the item's value, to be submitted if it is part of a
  {@link FormPanel}; cannot be <code>null</code>
  @param text   the text of the item to be added
  @param reload perform a 'material select' reload to update the DOM.