diff --git a/tests/data_mid_layer_tests/test_dataset.py b/tests/data_mid_layer_tests/test_dataset.py
index 055e603f3a..9eb2083aa7 100755
--- a/tests/data_mid_layer_tests/test_dataset.py
+++ b/tests/data_mid_layer_tests/test_dataset.py
@@ -98,19 +98,19 @@ def testTSDataset(self):
             print(data.shape)
             print(idx[i])
 
+
 class TestTSDataSampler(unittest.TestCase):
     def test_TSDataSampler(self):
         """
         Test TSDataSampler for issue #1716
         """
-        datetime_list = [
-            '2000-01-31', '2000-02-29', '2000-03-31', '2000-04-30', '2000-05-31'
-        ]
-        instruments = ['000001', '000002', '000003', '000004', '000005']
-        index = pd.MultiIndex.from_product([pd.to_datetime(datetime_list), instruments],
-                                           names=['datetime', 'instrument'])
+        datetime_list = ["2000-01-31", "2000-02-29", "2000-03-31", "2000-04-30", "2000-05-31"]
+        instruments = ["000001", "000002", "000003", "000004", "000005"]
+        index = pd.MultiIndex.from_product(
+            [pd.to_datetime(datetime_list), instruments], names=["datetime", "instrument"]
+        )
         data = np.random.randn(len(datetime_list) * len(instruments))
-        test_df = pd.DataFrame(data=data, index=index, columns=['factor'])
+        test_df = pd.DataFrame(data=data, index=index, columns=["factor"])
         dataset = TSDataSampler(test_df, datetime_list[0], datetime_list[-1], step_len=2)
         print()
         print("--------------dataset[0]--------------")
@@ -127,14 +127,13 @@ def test_TSDataSampler2(self):
         """
         Extra test TSDataSampler to prevent incorrect filling of nan for the values at the front
         """
-        datetime_list = [
-            '2000-01-31', '2000-02-29', '2000-03-31', '2000-04-30', '2000-05-31'
-        ]
-        instruments = ['000001', '000002', '000003', '000004', '000005']
-        index = pd.MultiIndex.from_product([pd.to_datetime(datetime_list), instruments],
-                                           names=['datetime', 'instrument'])
+        datetime_list = ["2000-01-31", "2000-02-29", "2000-03-31", "2000-04-30", "2000-05-31"]
+        instruments = ["000001", "000002", "000003", "000004", "000005"]
+        index = pd.MultiIndex.from_product(
+            [pd.to_datetime(datetime_list), instruments], names=["datetime", "instrument"]
+        )
         data = np.random.randn(len(datetime_list) * len(instruments))
-        test_df = pd.DataFrame(data=data, index=index, columns=['factor'])
+        test_df = pd.DataFrame(data=data, index=index, columns=["factor"])
         dataset = TSDataSampler(test_df, datetime_list[2], datetime_list[-1], step_len=3)
         print()
         print("--------------dataset[0]--------------")
@@ -146,6 +145,8 @@ def test_TSDataSampler2(self):
             self.assertFalse(np.isnan(dataset[1][i]))
         self.assertEqual(dataset[0][1], dataset[1][0])
         self.assertEqual(dataset[0][2], dataset[1][1])
+
+
 if __name__ == "__main__":
     unittest.main(verbosity=10)