Undo changes in test_api

tests/services/contents/test_api.py

@@ -17,6 +17,7 @@
 
 from ...utils import expected_http_error
 
+
 def notebooks_only(dir_model):
     return [nb for nb in dir_model['content'] if nb['type']=='notebook']
 
@@ -837,4 +838,4 @@ async def test_file_checkpoints(fetch, contents):
         method='GET'
     )
     cps = json.loads(r.body.decode())
-    assert cps == []
+    assert cps == []