docs: def execution_engine_model_changed(self, model, prop_name, info):
          """Active observation of state machine and show and hide widget. """
          if not self._view_initialized:
              return
  
          active_sm_id = rafcon.gui.singleton.state_machine_manager_model.state_machine_manager.active_state_machine_id
          if active_sm_id is None:
              # relieve all state machines that have no active execution and hide the widget
              self.disable()
          else:
              # observe all state machines that have an active execution and show the widget
              self.check_configuration()