def countdown(self):
        with self._cond:
            self._count -= 1
            if self._count <= 0:
                self._cond.notify_all()
Internal helper to check this property for specific requirements.
dataset/ETHPy150Open openstack/taskflow/taskflow/types/latch.py/Latch.countdown--crossover with--dataset/ETHPy150Open GoogleCloudPlatform/datastore-ndb-python/ndb/model.py/Property._check_property