def test_kwargs() -> None:
    'Test functionality when signature uses ``**kwargs``. '

    @argcomb(a='b')
    def f(**kwargs: Any) -> None:
        ...
    f(a=1, b=1)
    f(b=1, c=1)
    with pytest.raises(InvalidArgumentCombination):
        f(a=1)
Test functionality when signature uses ``**kwargs``.
def test_kwargs() -> None:
    ' '

    @argcomb(a='b')
    def f(**kwargs: Any) -> None:
        ...
    f(a=1, b=1)
    f(b=1, c=1)
    with pytest.raises(InvalidArgumentCombination):
        f(a=1)