code: def add_data_item(self, data_item: DataItem) -> None:
          
          display_item = data_item._data_item.container.get_display_item_for_data_item(data_item._data_item) if data_item._data_item.container else None
          if display_item:
              self.__data_group.append_display_item(display_item)
docs: Add a data item to the group.
  
          :param data_item: The :py:class:`nion.swift.Facade.DataItem` object to add.
  
          .. versionadded:: 1.0
  
          Scriptable: Yes