Doxygen for Python module split into multiple files

I am using Doxygen to document a Python project. This project includes a module that is split into multiple files. I needed to do this for maintainability. Some of the classes in the module are very large with complex implementations. If I had to combine them all into one file, this file would become unmanageably large, over 10,000 lines. So I split them into many files and then __init__.py imported all files into the parent module. This works well: the code is maintained and users can import everything with a single import statement.

But Doxygen doesn't know about this. It displays all classes as divided into many modules. I don't want users to know that all of these modules exist. This is just detailing to keep the code simpler. How can I create documentation that matches the intended API, with all the classes shown as one module?