(someone on the BaseX team will surely correct where I get this wrong, so...) as far as I know, many/most/all of the BaseX builtin modules are written in Java, not XQuery, so I don't know that there are modules to inspect, so to speak. However, late last year there was some discussion on the list along these same lines and Christian wrote up an XQuery script to generate xqDoc output from the wiki [1]. 

Maybe that would be helpful for your project?

Best, 

Bridger

[1] https://github.com/BaseXdb/basex-dist/blob/master/wiki2xqdoc.xq