Revise comment

aleksis/apps/chronos/schema/__init__.py

@@ -163,8 +163,8 @@ class SubstitutionBatchCreateOrUpdateMutation(graphene.Mutation):
     def create_or_update(cls, info, substitution):
         _id = substitution.id
 
-        # Sadly, we can't use the update_or_create method since create_defaults
-        # is only introduced in Django 5.0
+        # Sadly, we can't use the update_or_create method since we can't check
+        # different permissions depending on the operation with it.
         if _id.startswith("DUMMY"):
             dummy, amended_lesson_event_id, datetime_start_iso, datetime_end_iso = _id.split(";")
             amended_lesson_event = LessonEvent.objects.get(id=amended_lesson_event_id)