diff --git a/deepmd/pt/model/task/property.py b/deepmd/pt/model/task/property.py
index 233cd3ddb2..7f0796d08f 100644
--- a/deepmd/pt/model/task/property.py
+++ b/deepmd/pt/model/task/property.py
@@ -2,7 +2,7 @@
 import logging
 from typing import (
     Optional,
-    Union
+    Union,
 )
 
 import torch