This page:

https://cloud.google.com/appengine/docs/python/multitenancy/#Python_Building_a_multitenant_application_with_the_Namespaces_API

refers to a Python Namespacing example with this link:

https://github.com/GoogleCloudPlatform/python-docs-samples/tree/master/appengine/multitenancy

Python App Engine: appengine-multitenancy – A namespace-aware sample guestbook application.

and that link 404's...