diff --git a/tosfs/core.py b/tosfs/core.py
index 324a8d9..184177a 100644
--- a/tosfs/core.py
+++ b/tosfs/core.py
@@ -846,9 +846,11 @@ def isdir(self, path: str) -> bool:
         except TosServerError as e:
             if e.status_code == TOS_SERVER_STATUS_CODE_NOT_FOUND:
                 return False
-            if (self._get_bucket_type(bucket) == TOS_BUCKET_TYPE_HNS
+            if (
+                self._get_bucket_type(bucket) == TOS_BUCKET_TYPE_HNS
                 and e.status_code == CONFLICT_CODE
-                and e.header._store["x-tos-ec"][1] == "0026-00000020"):
+                and e.header._store["x-tos-ec"][1] == "0026-00000020"
+            ):
                 out = retryable_func_executor(
                     lambda: self.tos_client.list_objects_type2(
                         bucket,