Return callback to unsubscribe to entity (#93)

pylutron/__init__.py

@@ -632,7 +632,7 @@ def _dispatch_event(self, event: LutronEvent, params: Dict):
     for handler, context in self._subscribers:
       handler(self, context, event, params)
 
-  def subscribe(self, handler: LutronEventHandler, context):
+  def subscribe(self, handler: LutronEventHandler, context) -> Callable[[], None]:
     """Subscribes to events from this entity.
 
     handler: A callable object that takes the following arguments (in order)
@@ -642,8 +642,10 @@ def subscribe(self, handler: LutronEventHandler, context):
              params: a dict of event-specific parameters
 
     context: User-supplied, opaque object that will be passed to handler.
+    Returns: A callable that can be used to unsubscribe from the event.
     """
     self._subscribers.append((handler, context))
+    return lambda: self._subscribers.remove((handler, context))
 
   def handle_update(self, args):
     """The handle_update callback is invoked when an event is received