Tokio_proto multiplex

I looked into the tokio library a bit, and multiplex seems quite interesting.
The problem is that I couldn't really understand what's going on there, and couldn't also find some basic example of using it.
Can someone please help me with this? maybe write an example which shows how to use multiplex with it's basic functionality?

I've heard the tokio devs are very responsive on their gittr, you might want to ask in there as well.