Fix teacher timetable

aleksis/apps/chronos/managers.py

@@ -866,10 +866,10 @@ class LessonEventQuerySet(PolymorphicQuerySet):
     """Queryset with special query methods for lesson events."""
 
     def for_teacher(self, teacher: Union[int, Person]):
-        amended = objs.filter(Q(amended_by__isnull=False) & (Q(teachers=teacher))).values_list(
+        amended = self.filter(Q(amended_by__isnull=False) & (Q(teachers=teacher))).values_list(
             "amended_by__pk", flat=True
         )
-        return objs.filter(Q(teachers=teacher) | Q(pk__in=amended)).distinct()
+        return self.filter(Q(teachers=teacher) | Q(pk__in=amended)).distinct()
 
     def for_group(self, group: Union[int, Group]):
         amended = self.filter(