diff --git a/xarray/core/resample_cftime.py b/xarray/core/resample_cftime.py
index 2c9b13151ab..983f31decc5 100644
--- a/xarray/core/resample_cftime.py
+++ b/xarray/core/resample_cftime.py
@@ -75,11 +75,9 @@ class CFTimeGrouper:
 
     def __init__(
         self,
-        freq: str
-        | datetime.timedelta
-        | pd.Timedelta
-        | pd.DateOffset
-        | BaseCFTimeOffset,
+        freq: (
+            str | datetime.timedelta | pd.Timedelta | pd.DateOffset | BaseCFTimeOffset
+        ),
         closed: SideOptions | None = None,
         label: SideOptions | None = None,
         origin: str | CFTimeDatetime = "start_day",