Attaches the option ``nested`` with its *default* value to the
    keyword arguments when the option does not exist. All positional
    arguments and keyword arguments are forwarded unchanged.

def nested_option(default=False):
    """ Attaches the option ``nested`` with its *default* value to the
    keyword arguments when the option does not exist. All positional
    arguments and keyword arguments are forwarded unchanged.
    """

    def decorator(method):
        @wraps(method)
        def wrapper(*args, **kwargs):
            option = Option.nested.value
            kwargs[option] = kwargs.get(option, bool(default))
            return method(*args, **kwargs)

        return wrapper

    return decorator