--- a/mercurial/stabletailgraph/stabletailsort.py	Mon Sep 16 15:36:44 2024 +0200
+++ b/mercurial/stabletailgraph/stabletailsort.py	Thu Sep 12 16:27:58 2024 -0400
@@ -19,6 +19,8 @@
 optimised to operate on large production graphs.
 """
 
+from __future__ import annotations
+
 import itertools
 from ..node import nullrev
 from .. import ancestor