diff --git a/examples/rolling_process_data/workflow.py b/examples/rolling_process_data/workflow.py
index 9b61af47e..9dd4285da 100644
--- a/examples/rolling_process_data/workflow.py
+++ b/examples/rolling_process_data/workflow.py
@@ -12,11 +12,12 @@ from qlib.contrib.data.handler import Alpha158
 from qlib.utils import exists_qlib_data, init_instance_by_config
 from qlib.tests.data import GetData
 
+
 class RollingDataWorkflow(object):
 
     MARKET = "csi300"
     start_time = "2010-01-01"
-    end_time = "2019-12-31" 
+    end_time = "2019-12-31"
     rolling_cnt = 5
 
     def _init_qlib(self):
@@ -27,7 +28,7 @@ class RollingDataWorkflow(object):
             print(f"Qlib data is not found in {provider_uri}")
             GetData().qlib_data(target_dir=provider_uri, region=REG_CN)
         qlib.init(provider_uri=provider_uri, region=REG_CN)
-    
+
     def _dump_pre_handler(self, path):
         handler_config = {
             "class": "Alpha158",
@@ -51,13 +52,13 @@ class RollingDataWorkflow(object):
         self._dump_pre_handler("pre_handler.py")
         pre_handler = self._load_pre_handler("pre_handler.py")
 
-        train_start_time = (2010,1,1)
-        train_end_time = (2012,12,31)
-        valid_start_time = (2013,1,1)
-        valid_end_time = (2013,12,31)
-        test_start_time = (2014,1,1)
-        test_end_time = (2014,12,31)
-        
+        train_start_time = (2010, 1, 1)
+        train_end_time = (2012, 12, 31)
+        valid_start_time = (2013, 1, 1)
+        valid_end_time = (2013, 12, 31)
+        test_start_time = (2014, 1, 1)
+        test_end_time = (2014, 12, 31)
+
         dataset_config = {
             "class": "DatasetH",
             "module_path": "qlib.data.dataset",
@@ -70,9 +71,9 @@ class RollingDataWorkflow(object):
                         "end_time": datetime(*test_end_time),
                         "fit_start_time": datetime(*train_start_time),
                         "fit_end_time": datetime(*train_end_time),
-                        "data_loader_kwargs":{
+                        "data_loader_kwargs": {
                             "handler_config": pre_handler,
-                        }
+                        },
                     },
                 },
                 "segments": {
@@ -94,14 +95,23 @@ class RollingDataWorkflow(object):
                         "end_time": datetime(test_end_time[0] + 1, *test_end_time[1:]),
                     },
                     segment_kwargs={
-                        "train": (datetime(train_start_time[0] + 1, *train_start_time[1:]), datetime(train_end_time[0], *train_end_time[1:])),
-                        "valid": (datetime(valid_start_time[0] + 1, *valid_start_time[1:]), datetime(valid_end_time[0], *valid_end_time[1:])),
-                        "test": (datetime(test_start_time[0] + 1, *test_start_time[1:]), datetime(test_end_time[0], *test_end_time[1:])),
+                        "train": (
+                            datetime(train_start_time[0] + 1, *train_start_time[1:]),
+                            datetime(train_end_time[0], *train_end_time[1:]),
+                        ),
+                        "valid": (
+                            datetime(valid_start_time[0] + 1, *valid_start_time[1:]),
+                            datetime(valid_end_time[0], *valid_end_time[1:]),
+                        ),
+                        "test": (
+                            datetime(test_start_time[0] + 1, *test_start_time[1:]),
+                            datetime(test_end_time[0], *test_end_time[1:]),
+                        ),
                     },
                 )
 
-            dtrain, dvalid, dtest  = dataset.prepare(["train", "valid", "test"])
-            
+            dtrain, dvalid, dtest = dataset.prepare(["train", "valid", "test"])
+
 
 if __name__ == "__main__":
 
@@ -147,4 +157,3 @@ if __name__ == "__main__":
     }
 
     dataset = init_instance_by_config(task["dataset"])
-