Mux plugin help

I am trying to build a mux plugin but I find difficult to access to the sink pads and check the buffers is there a documentation or tutorial that explain how to do it?
P.D: I was checking the rust plugin tutorias but there are just src element,sink element and filter elements

You need to subclass gst aggregatior most likely. I would reccomend reading a rust muxer’s code, they are pretty straightforward to follow.