diff --git a/qlib/contrib/model/pytorch_sandwich.py b/qlib/contrib/model/pytorch_sandwich.py
index 4a61be5e1d..020c736fd3 100644
--- a/qlib/contrib/model/pytorch_sandwich.py
+++ b/qlib/contrib/model/pytorch_sandwich.py
@@ -300,10 +300,15 @@ def test_epoch(self, data_x, data_y):
         return np.mean(losses), np.mean(scores)
 
     def fit(
-        self, dataset: DatasetH, evals_result=dict(), save_path=None,
+        self,
+        dataset: DatasetH,
+        evals_result=dict(),
+        save_path=None,
     ):
         df_train, df_valid, df_test = dataset.prepare(
-            ["train", "valid", "test"], col_set=["feature", "label"], data_key=DataHandlerLP.DK_L,
+            ["train", "valid", "test"],
+            col_set=["feature", "label"],
+            data_key=DataHandlerLP.DK_L,
         )
         if df_train.empty or df_valid.empty:
             raise ValueError("Empty data from dataset, please check your dataset config.")