fix format

Author: sycai

bigframes/dataframe.py

@@ -891,7 +891,7 @@ def __delitem__(self, key: str):
 
     def __setitem__(
         self,
-        key: str | list[str] |  pandas.Index,
+        key: str | list[str] | pandas.Index,
         value: SingleItemValue | MultiItemValue,
     ):
         if isinstance(key, (list, pandas.Index)):

tests/system/small/test_dataframe.py

@@ -1198,8 +1198,10 @@ def test_assign_new_column_w_setitem_list_error(scalars_dfs):
             ["new_col", "new_col_too"], [1, 2], id="sequence_to_full_new_column"
         ),
         pytest.param(
-            pd.Index(("new_col", "new_col_too")), [1, 2], id="sequence_to_full_new_column_as_index"
-        )
+            pd.Index(("new_col", "new_col_too")),
+            [1, 2],
+            id="sequence_to_full_new_column_as_index",
+        ),
     ],
 )
 def test_setitem_multicolumn_with_literals(scalars_dfs, key, value):