docs: def update_core_element_lists(self):
          """ Maintains inner lists of selected elements with a specific core element class """
          def get_selected_elements_of_core_class(core_class):
              return set(element for element in self._selected if isinstance(element.core_element, core_class))
          self._states = get_selected_elements_of_core_class(State)
          self._transitions = get_selected_elements_of_core_class(Transition)
          self._data_flows = get_selected_elements_of_core_class(DataFlow)
          self._input_data_ports = get_selected_elements_of_core_class(InputDataPort)
          self._output_data_ports = get_selected_elements_of_core_class(OutputDataPort)
          self._scoped_variables = get_selected_elements_of_core_class(ScopedVariable)
          self._outcomes = get_selected_elements_of_core_class(Outcome)