Overpass: Returning tags only for certain nodes

I would like to retrieve bus lines in my area, but my current method returns a lot of tags I don't need for nodes like pedestrian crossings or traffic lights.

I understand that using named sets and more than one out statement would be the way to only print tags for nodes that are public_transport=*; unfortunately, I can't find any examples of someone doing this. I've read the language guide on the wiki, but it doesn't really seem to explain how to do this.

I would be very happy to receive some help, links to examples, or even a link to the right place in the documentation.