code: function (item) {
          if (Item.isItem(item) || ItemGroup.isItemGroup(item)) { return item; }
  
          return item && item.item ? new ItemGroup(item) : new Item(item);
      }
docs: Iterator function to update an itemgroup's item array with appropriate objects from definition.
  
  @private
  @this {ItemGroup}
  @param {Object} item - the definition of an item or group
  @returns {ItemGroup|Item}
  @note
  This function is intended to be used in scope of an instance of a {@link ItemGroup).