From recent issue on GitHub:

Yep, that will be a part of Maid v0.4.0.

I’ve released some alpha builds (which are probably closer to beta quality), if you’d like to start playing with that functionality. I’d like to do some more testing to make sure everything works as expected, has a nice syntax, etc. Unfortunately, we’re in the middle of moving to a new place, so my time is limited right now.

Beta testing is always very appreciated, so if you have comments on how this feature works, please share! The method you want is probably where_content_type(). There are some examples in the documentation.