As a newbie to your world, I may see things that others don’t. If I’m wrong, please be nice and correct me.
At the client documentation hosted at: http://pythonhosted.org/couchbase/api/results.html#couchbase.result.Result
ValueResult or its super classes do not list the CAS property.
In my case, a ValueResult looks like:
Looking at your code, CAS should probably be documented in Result or OperationResult.