docs: def copy_action_callback(self, *event):
          """Callback method for copy action"""
          if react_to_event(self.view, self.tree_view, event) and self.active_entry_widget is None:
              sm_selection, sm_selected_model_list = self.get_state_machine_selection()
              # only list specific elements are copied by widget
              if sm_selection is not None:
                  sm_selection.set(sm_selected_model_list)
                  global_clipboard.copy(sm_selection)
                  return True