def anno_parser(func):
    "Look at params (annotated with `Param`) in func and return an `ArgumentParser`"
    p = ArgumentParser(description=func.__doc__)
    for k,v in inspect.signature(func).parameters.items():
        param = func.__annotations__.get(k, Param())
        kwargs = param.kwargs
        if v.default != inspect.Parameter.empty: kwargs['default'] = v.default
        p.add_argument(f"{param.pre}{k}", **kwargs)
    return p