Add type hints to all (public API) code make the distribution PEP 561 compliant. This allows mypy (and other tools?) to find the type hints and use them in linting.

In practice, add py.typed file to statsd package, and include it in the package:

setup(
    package_data={'statsd': ['py.typed']},
    zip_safe=False,  # not needed with wheels, AFAIK
)

PEP 561: https://www.python.org/dev/peps/pep-0561/