Per PEP 561 package maintainers can distribute type information with their libraries. Since you've gone to the effort of adding type hints to your code, if you add a py.typed to the codebase and include it in the package, mypy will understand that it can read type information from your source code.

ATM, I need to add an exception for this lib so that our mypy checks pass, which is a shame, given that the type information is present.

https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports