def METHOD_NAME(self) -> None:
    with self._lock:
        active = list(self.active_containers)
    for c in active:
        print("killing container %s" % (c,))
        subprocess.run(
            [
                "docker",
                "kill",
                c,
            ],
            stdout=subprocess.DEVNULL,
        )
        with self._lock:
            self.active_containers.remove(c)