Union[str, None],
        Doc(
            """
            'Blacklist' validation step. The vanilla parameter field will be the
            single one of the alias' or set of aliases' fields and all the other
            fields will be ignored at serialization time.
            """
        ),
    ] = None,
    title: Annotated[
        Optional[str],
        Doc(
            """
            Human-readable title.

    )
    def post_router(item1: Item, item2: Item):
        return item1, item2  # pragma: nocover

    @sub_router.post(
        "/subrouter",
        response_model=List[Item],
        responses={404: {"model": List[Message]}},
    )
    def post_subrouter(item1: Item, item2: Item):
        return item1, item2  # pragma: nocover

    router.include_router(sub_router)