style fixes

Author: vgvoleg

tests/query/test_query_session.py

@@ -139,4 +139,4 @@ def cancel(self):
         assert "first response attach stream thread" not in thread_names
         assert "attach stream thread" not in thread_names
 
-        _check_session_state_empty(session)
+        _check_session_state_empty(session)