diff --git a/ignite/metrics/clustering/silhouette_score.py b/ignite/metrics/clustering/silhouette_score.py
index 9498bb5479b..39b28c5d040 100644
--- a/ignite/metrics/clustering/silhouette_score.py
+++ b/ignite/metrics/clustering/silhouette_score.py
@@ -1,4 +1,4 @@
-from typing import Any, Callable, Union, Optional
+from typing import Any, Callable, Optional, Union
 
 import torch
 from torch import Tensor