Merge pull request #19 from Zsailer/bugs

Fix minor bugs in Listeners API

jupyter_events/logger.py

@@ -255,11 +255,6 @@ def add_listener(
         if not callable(listener):
             raise TypeError("`listener` must be a callable")
 
-        if schema_id not in self.schemas:
-            raise SchemaNotRegistered(
-                "The schema given for this listener has not be registered yet."
-            )
-
         signature = inspect.signature(listener)
 
         async def listener_signature(
@@ -277,7 +272,7 @@ async def listener_signature(
                     self._modified_listeners[schema_id].add(listener)
                     return
                 self._unmodified_listeners[schema_id].add(listener)
-            for id in self.listeners:
+            for id in self.schemas.schema_ids:
                 if schema_id is None or id == schema_id:
                     if modified:
                         self._modified_listeners[id].add(listener)