Fix linting errors

tracetools_test/test/test_subscription.py

@@ -1,8 +1,9 @@
 import unittest
+
 from tracetools_test.utils import (
+    cleanup_trace,
     get_trace_event_names,
     run_and_trace,
-    cleanup_trace,
 )
 
 BASE_PATH = '/tmp'
@@ -12,6 +13,7 @@ subscription_creation_events = [
     'ros2:rclcpp_subscription_callback_added',
 ]
 
+
 class TestSubscription(unittest.TestCase):
 
     def test_creation(self):