docs: def recursively_preempt_states(self):
          """ Preempt the state and all of it child states.
          """
          super(ContainerState, self).recursively_preempt_states()
          # notify the transition condition variable to let the state instantaneously stop
          self._transitions_cv.acquire()
          self._transitions_cv.notify_all()
          self._transitions_cv.release()
          for state in self.states.values():
              state.recursively_preempt_states()