diff --git a/examples/high_freq/highfreq_processor.py b/examples/high_freq/highfreq_processor.py
index d2ffe41ce..d71cd2e85 100644
--- a/examples/high_freq/highfreq_processor.py
+++ b/examples/high_freq/highfreq_processor.py
@@ -57,7 +57,7 @@ class HighFreqNorm(Processor):
             part_values[slice3] = -3.5
         # print("start_call_feature_reshape")
         idx = df_features.index.droplevel("datetime").drop_duplicates()
-        idx.set_names(['instrument', 'datetime'], inplace=True)
+        idx.set_names(["instrument", "datetime"], inplace=True)
         feat = df_values[:, [0, 1, 2, 3, 4, 10]].reshape(-1, 6 * 240)
         feat_1 = df_values[:, [5, 6, 7, 8, 9, 11]].reshape(-1, 6 * 240)
         df_new_features = pd.DataFrame(
diff --git a/examples/high_freq/workflow.py b/examples/high_freq/workflow.py
index 112e99070..8304cf26a 100644
--- a/examples/high_freq/workflow.py
+++ b/examples/high_freq/workflow.py
@@ -147,14 +147,13 @@ if __name__ == "__main__":
     }
     ##=============load the calendar for cache=============
     Cal.calendar(freq="1min")
-    Cal.get_calendar_day(freq="1min") 
-    
+    Cal.get_calendar_day(freq="1min")
 
     ##=============get data=============
     dataset = init_instance_by_config(task["dataset"])
     dataset_backtest = init_instance_by_config(task["dataset_backtest"])
-    xtrain, xtest = dataset.prepare(['train', 'test'])
-    backtest_train, backtest_test = dataset_backtest.prepare(['train', 'test'])
+    xtrain, xtest = dataset.prepare(["train", "test"])
+    backtest_train, backtest_test = dataset_backtest.prepare(["train", "test"])
     print(xtrain, xtest)
     print(backtest_train, backtest_test)
     del xtrain, xtest
@@ -172,15 +171,13 @@ if __name__ == "__main__":
 
     file_dataset_backtest = open("dataset_backtest.pkl", "rb")
     dataset_backtest = pickle.load(file_dataset_backtest)
-    
+
     file_dataset_backtest.close()
 
     ##=============reload_dataset=============
     dataset.init(init_type=DataHandlerLP.IT_LS)
     dataset_backtest.init(init_type=DataHandlerLP.IT_LS)
 
-
-
     ##=============reinit qlib=============
     qlib.init(
         provider_uri=provider_uri,
@@ -190,12 +187,12 @@ if __name__ == "__main__":
         auto_mount=False,
     )
 
-    Cal.calendar(freq="1min") #load the calendar for cache
-    Cal.get_calendar_day(freq="1min") #load the calendar for cache
+    Cal.calendar(freq="1min")  # load the calendar for cache
+    Cal.get_calendar_day(freq="1min")  # load the calendar for cache
 
     ##=============test dataset
-    xtrain, xtest = dataset.prepare(['train', 'test'])
-    backtest_train, backtest_test = dataset_backtest.prepare(['train', 'test'])
+    xtrain, xtest = dataset.prepare(["train", "test"])
+    backtest_train, backtest_test = dataset_backtest.prepare(["train", "test"])
 
     print(xtrain, xtest)
     print(backtest_train, backtest_test)
diff --git a/qlib/data/ops.py b/qlib/data/ops.py
index 62df98647..66e588be1 100644
--- a/qlib/data/ops.py
+++ b/qlib/data/ops.py
@@ -1479,7 +1479,7 @@ Operators = OpsWrapper()
 def register_all_ops(C):
     """register all operator"""
     logger = get_module_logger("ops")
-    
+
     Operators.reset()
     Operators.register(OpsList)