Inspectdb command for migrating from Google cloud ndb / Datastore

[ipcam...@gmail.com]

Thanks for building and maintaining this library!

I'm currently using Appengine with the Datastore using the Google Cloud NDB client library. I suspect it isn't possible to migrate an existing application currently - is that the case? 

I would love to migrate the application to Django. To make migration easier it would be nice to have an `inspectdb` command like I can use for MySQL or PostgreSQL to create Django models on top of an existing Datastore.