def METHOD_NAME(event_bus: EventBus, processor):
    """Test unsubscribe idempotency."""
    event_bus.subscribe(re.compile(".*"), processor)
    event_bus.unsubscribe(re.compile(".*"), processor)
    assert not event_bus.topic_patterns_to_subscribers
    event_bus.unsubscribe(re.compile(".*"), processor)
    assert not event_bus.topic_patterns_to_subscribers