code: def add_machine(self, machine):
          
          self._logger.debug('Adding machine {} to driver'.format(machine.id))
          machine._driver = self
          machine._reset()
          if machine.id is not None:
              # TODO warning when STM already registered
              Driver._stms_by_id[machine.id] = machine
              self._add_event(event_id=None, args=[], kwargs={}, stm=machine)
docs: Add the state machine to this driver.