`mypy --strict` fails with `Name "betterproto.ServiceStub" is not defined`

Summary

mypy --strict fails with Name "betterproto.ServiceStub" is not defined

Reproduction Steps

Generate some gRPC files from some proto files
Run mypy on the generated code

Expected Results

mypy passes.

Actual Results

error: Name "betterproto.ServiceStub" is not defined  [name-defined]

Where the stub class is defined in the generated code.

I see the symbol is imported in https://github.com/danielgtaylor/python-betterproto/blob/master/src/betterproto/__init__.py, but it seems like mypy needs imported symbols to be explicitly exported, probably via __all__ or using from x import y as y (see https://peps.python.org/pep-0484/#stub-files).

System Information

$ protoc --version; python --version; pip show betterproto; pip show grpcio-tools
bash: protoc: command not found
Python 3.11.9
Name: betterproto
Version: 2.0.0b6
Location: /home/luca/devel/frequenz-microgrid-betterproto/.direnv/python-3.11.9/lib/python3.11/site-packages
Requires: grpclib, python-dateutil
Required-by: frequenz-microgrid-betterproto
Name: grpcio-tools
Version: 1.63.0
Location: /home/luca/devel/setuptools-betterproto/.direnv/python-3.11/lib/python3.11/site-packages
Requires: grpcio, protobuf, setuptools

(I'm using grpcio-tools to generate the files, not protoc)

Checklist

[X] I have searched the issues for duplicates.
[X] I have shown the entire traceback, if possible.
[X] I have verified this issue occurs on the latest prelease of betterproto which can be installed using pip install -U --pre betterproto, if possible.

danielgtaylor / python-betterproto

`mypy --strict` fails with `Name "betterproto.ServiceStub" is not defined` #577