Support type checking II

https://docs.python.org/3/howto/descriptor.html#descriptor-protocol
https://mypy.readthedocs.io/en/stable/more_types.html#function-overloading
https://github.com/python/typeshed/blob/master/stdlib/functools.pyi#L142

This feels less obscure than the "as" syntax.
https://mypy.readthedocs.io/en/stable/config_file.html#confval-implicit_reexport

If set the flag causes tests and examples to be included in the wheel.

Without this the type checker complains about "implicit re-export".
https://mypy.readthedocs.io/en/stable/config_file.html#confval-implicit_reexport