Common: Add comment about subscribing to all topics in PyPubSubEventQueue

monkey/common/event_queue/pypubsub_event_queue.py

@@ -12,6 +12,12 @@ class PyPubSubEventQueue(IEventQueue):
         self._pypubsub_publisher = pypubsub_publisher
 
     def subscribe_all(self, subscriber: Callable[[AbstractEvent], None]):
+        # From the documentation (https://pypubsub.readthedocs.io/en/v4.0.3/usage/
+        # usage_advanced_debug.html#listen-for-messages-from-all-topics):
+        # "PyPubSub defines a special topic named pub.ALL_TOPICS. A listener that subscribes
+        # to this topic will receives all messages of every topic. By default, the listener
+        # will not receive any data since pub.ALL_TOPICS is the parent of all root topics (...)"
+
         self._pypubsub_publisher.subscribe(
             listener=subscriber, topicName=self._pypubsub_publisher.ALL_TOPICS
         )