[HACKERS] Example Custom Scan Provider Implementation?

Does anyone know of a simple, example Custom Scan Provider implementation for 9.6+?  

I found pg_strom by searching GitHub.  Its gpuscan.c looks like maybe it implements a pattern similar to what I want to do, but there's a lot of extraneous (to me) stuff to parse through.

I'm kinda surprised there isn't an example in contrib/, actually.

Thanks for your time!

eric