Type Diagrams (like UML Class Diagrams for OOPs)


I am developing a moderately complicated system in Julia. There will be a lot of modules that can be plugged in and off; various combinations of these modules will result in various algorithms. The modules are mostly type-dispatched functions. So there will be a few Types too that dictate module behaviour. (Some of the types would be singletons.)
Before I start coding I want to draw a huge diagram so that I get my abstractions right. So is there something like UML Class Diagrams for languages like Julia. Or is there a good example of a document that has a bunch of boxes and lines representing, types, methods, etc.