diff --git a/sqlalchemy_utils/observer.py b/sqlalchemy_utils/observer.py
index 69a2053..ce5351c 100644
--- a/sqlalchemy_utils/observer.py
+++ b/sqlalchemy_utils/observer.py
@@ -317,6 +317,7 @@ class PropertyObserver(object):
             for callback, objs in callback_objs.items():
                 callback(root_obj, *[objs[i] for i in range(len(objs))])
 
+
 observer = PropertyObserver()