def METHOD_NAME(
    self, ms_before_unhealthy: int
) -> typing.List[TaskRunner]:
    unhealthy_threads = []
    healthy_threshold = timezone.now() - timedelta(milliseconds=ms_before_unhealthy)
    for thread in self._threads:
        if (
            not thread.is_alive()
            or not thread.last_checked_for_tasks
            or thread.last_checked_for_tasks < healthy_threshold
        ):
            unhealthy_threads.append(thread)
    return unhealthy_threads