diff --git a/visualdl/backend/test.py b/visualdl/backend/test.py
index f0cd54d65325c04e3d5f8da19019f8f698329a59..8755ae7ff8a23587756fa8a8b76d568365c1744c 100644
--- a/visualdl/backend/test.py
+++ b/visualdl/backend/test.py
@@ -1,10 +1,12 @@
 import sys
 import unittest
+
 sys.path.append('../../build')
 import core
 
 im = core.im()
 
+
 class StorageTester(unittest.TestCase):
     def setUp(self):
         self.storage = im.storage()