def relieve_state_machines(self, model, prop_name, info):
        """ The method relieves observed models before those get removed from the list of state_machines hold by
        observed StateMachineMangerModel. The method register as observer of observable
        StateMachineMangerModel.state_machines."""
        if info['method_name'] == '__setitem__':
            pass
        elif info['method_name'] == '__delitem__':
            self.relieve_model(self.state_machine_manager_model.state_machines[info['args'][0]])
            self.logger.info(NotificationOverview(info))
        else:
            self.logger.warning(NotificationOverview(info))