OOP & Design Patterns - Observer Pattern - Event System, Publish-Subscribe
Consider the following thread-safe observer pattern code snippet. What will be the output after these operations?
```python
subject = Subject()
obs = Observer('Obs')
subject.subscribe(obs, 'eventX')
subject.unsubscribe(obs, 'eventX')
subject.notify('eventX', 'Test')
```
Assuming notify calls update on all subscribed observers for the event type.