I find it frustrating that it's not made clear upfront that Walkmod is only for Java. In fact, it's not really made clear anywhere I can see so I'm not 100% sure that's correct but it seems to be the case.
From their GitHub README [1] (I'm not affiliated):
"Walkmod can support with any programing language if a set of interfaces are implemented as a third party plugin. The first (and current) supported language is Java."
It would be nice to write another plugin for something else like Python or C++. For example in the UML diagram I saw something called "JavadocComment" which immediately puts me off writing a plugin because it looks like I would have to follow this even for a non-Java language.
"Walkmod can support with any programing language if a set of interfaces are implemented as a third party plugin. The first (and current) supported language is Java."
[1] https://github.com/rpau/walkmod-core