diff --git a/backend/app/repositories/ownership_log_repository.py b/backend/app/repositories/ownership_log_repository.py
index d47447e..c5bb7ab 100644
--- a/backend/app/repositories/ownership_log_repository.py
+++ b/backend/app/repositories/ownership_log_repository.py
@@ -40,9 +40,7 @@ def list_by_ref(
     return list(session.execute(stmt).all())
 
 
-def count_by_ref(
-    session: Session, *, owner_type: int, ref_column, ref_id: int
-) -> int:
+def count_by_ref(session: Session, *, owner_type: int, ref_column, ref_id: int) -> int:
     """统计某引用对象的归属留痕总数，供分页使用。"""
     stmt = select(func.count(OwnershipChangeLog.id)).where(
         OwnershipChangeLog.owner_type == owner_type,
diff --git a/backend/app/services/rating_service.py b/backend/app/services/rating_service.py
index 4fcae4e..90110d3 100644
--- a/backend/app/services/rating_service.py
+++ b/backend/app/services/rating_service.py
@@ -217,7 +217,10 @@ def update_grade(
             raise NotFoundError("评级等级不存在")
 
         _ensure_no_overlap(
-            rating_repository.list_all(session, for_update=True), new_min, new_max, exclude_id=grade_id
+            rating_repository.list_all(session, for_update=True),
+            new_min,
+            new_max,
+            exclude_id=grade_id,
         )
         existed = rating_repository.get_by_name(session, payload.grade_name)
         if existed is not None and existed.id != grade_id: