Fix Workouts

backend/secfit/workouts/mixins.py

@@ -3,7 +3,7 @@ Mixins for the workouts application
 """
 
 
-class CreateListModelMixin(object):
+class CreateListModelMixin:
     """Mixin that allows to create multiple objects from lists.
     Taken from https://stackoverflow.com/a/48885641
     """