[5.0.x] Applied Black's 2024 stable style.

https://github.com/psf/black/releases/tag/24.1.0

Backport of 305757aec1 from main

tests/model_inheritance_regress/tests.py

@@ -1,6 +1,7 @@
 """
 Regression tests for Model inheritance behavior.
 """
+
 import datetime
 from operator import attrgetter
 from unittest import expectedFailure