async (motorengine)

I'm trying to get a stack of `Sanic`, `mongodb` and `graphql` to work. All async..
I can do mongo async using https://github.com/heynemann/motorengine, but then I have no way of using `graphene-mongo` as it wants a valid `Mongoengine Model`.

I can't find any issues on this in this repo, so I might be getting this wrong, but is there plans for supporting async? Or anyway I can hack it in using the current `graphene-mongo`?

Start by reviewing how graphene-mongo currently depends on MongoEngine Model objects, then compare that boundary with the Sanic, motorengine, and GraphQL stack described in the issue. The issue does not name files, tests, or an implementation entry point; done would require an agreed async-support scope or a documented way to use the existing integration asynchronously.

Written by the indexing model from the issue text.