Update base.py

StaffelnPersistentObject inherited from ovoo_base.VersionedObject
diff --git a/staffeln/objects/base.py b/staffeln/objects/base.py
index ea04b59..dd0730d 100755
--- a/staffeln/objects/base.py
+++ b/staffeln/objects/base.py
@@ -40,7 +40,7 @@
     OBJ_BASE_CLASS = StaffelnObject

 

 

-class StaffelnPersistentObject(object):

+class StaffelnPersistentObject(ovoo_base.VersionedObject):

     fields = {

         "created_at": ovoo_fields.DateTimeField(nullable=True),

         # "deleted_at": ovoo_fields.DateTimeField(nullable=True),