Walks the module contents, returns an index of all visited objects.

The return value is an instance of self._visitor_cls, usually: doc_generator_visitor.DocGeneratorVisitor

py_modules A list containing a single (short_name, module_object) pair. like [('tf',tf)].
visitor_cls A class, typically a subclass of doc_generator_visitor.DocGeneratorVisitor that acumulates the indexes of objects to document.
filters Filters passed to traverse. Executed before the accumulator (DocGeneratorVisitor). These filter the list of children.

The accumulator (DocGeneratorVisitor)