How to use the stone.ir.Void function in stone

def _get_api(self):
        # type () -> Api
        api = Api(version='0.1b1')
        api.route_schema = Struct(u'Route', 'stone_cfg', None)
        route1 = ApiRoute('get_metadata', 1, None)
        route1.set_attributes(None, ':route:`get_metadata`', Void(), Void(), Void(), {})
        route2 = ApiRoute('get_metadata', 2, None)
        route2.set_attributes(None, ':route:`get_metadata:2`', Void(), Int32(), Void(), {})
        ns = ApiNamespace('files')
        ns.add_route(route1)
        ns.add_route(route2)
        api.namespaces[ns.name] = ns
        return api, ns

def _get_api(self):
        # type () -> Api
        api = Api(version='0.1b1')
        api.route_schema = Struct(u'Route', 'stone_cfg', None)
        route1 = ApiRoute('get_metadata', 1, None)
        route1.set_attributes(None, ':route:`get_metadata`', Void(), Void(), Void(), {})
        route2 = ApiRoute('get_metadata', 2, None)
        route2.set_attributes(None, ':route:`get_metadata:2`', Void(), Int32(), Void(), {})
        ns = ApiNamespace('files')
        ns.add_route(route1)
        ns.add_route(route2)
        api.namespaces[ns.name] = ns
        return api, ns

def test_route_with_version_number(self):
        # type: () -> None

        route1 = ApiRoute('get_metadata', 1, None)
        route1.set_attributes(None, ':route:`get_metadata:2`', Void(), Void(), Void(), {})
        route2 = ApiRoute('get_metadata', 2, None)
        route2.set_attributes(None, None, Void(), Int32(), Void(), {})
        ns = ApiNamespace('files')
        ns.add_route(route1)
        ns.add_route(route2)

        result = self._evaluate_namespace(ns)

        expected = textwrap.dedent('''\
            def files_get_metadata(self):
                """
                :meth:`files_get_metadata_v2`

                :rtype: None
                """
                arg = None

def _get_api(self):
        # type () -> Api
        api = Api(version='0.1b1')
        api.route_schema = Struct(u'Route', 'stone_cfg', None)
        route1 = ApiRoute('get_metadata', 1, None)
        route1.set_attributes(None, ':route:`get_metadata`', Void(), Void(), Void(), {})
        route2 = ApiRoute('get_metadata', 2, None)
        route2.set_attributes(None, ':route:`get_metadata:2`', Void(), Int32(), Void(), {})
        ns = ApiNamespace('files')
        ns.add_route(route1)
        ns.add_route(route2)
        api.namespaces[ns.name] = ns
        return api, ns

def _get_api(self):
        # type () -> Api
        api = Api(version='0.1b1')
        api.route_schema = Struct(u'Route', 'stone_cfg', None)
        route1 = ApiRoute('get_metadata', 1, None)
        route1.set_attributes(None, ':route:`get_metadata`', Void(), Void(), Void(), {})
        route2 = ApiRoute('get_metadata', 2, None)
        route2.set_attributes(None, ':route:`get_metadata:2`', Void(), Int32(), Void(), {})
        ns = ApiNamespace('files')
        ns.add_route(route1)
        ns.add_route(route2)
        api.namespaces[ns.name] = ns
        return api, ns

def test_route_with_auth_mode1(self):
        # type: () -> None

        route1 = ApiRoute('get_metadata', 1, None)
        route1.set_attributes(None, ':route:`get_metadata:2`', Void(), Void(), Void(),
                              {'auth': 'app'})
        route2 = ApiRoute('get_metadata', 2, None)
        route2.set_attributes(None, None, Void(), Int32(), Void(),
                              {'auth': 'user, app'})
        ns = ApiNamespace('files')
        ns.add_route(route1)
        ns.add_route(route2)

        result = self._evaluate_namespace_with_auth_mode(ns, 'user')

        expected = textwrap.dedent('''\
            # ------------------------------------------
            # Routes in files namespace

            def files_get_metadata_v2(self):
                arg = None

def test_route_with_version_number(self):
        # type: () -> None

        route1 = ApiRoute('alpha/get_metadata', 1, None)
        route1.set_attributes(None, None, Void(), Void(), Void(), {})
        route2 = ApiRoute('alpha/get_metadata', 2, None)
        route2.set_attributes(None, None, Void(), Int32(), Void(), {})
        ns = ApiNamespace('files')
        ns.add_route(route1)
        ns.add_route(route2)

        result = self._evaluate_namespace(ns)

        expected = textwrap.dedent("""\
            alpha_get_metadata = bb.Route(
                'alpha/get_metadata',
                1,
                False,
                bv.Void(),
                bv.Void(),
                bv.Void(),
                {},
            )

with self.indent():
                            self.emit(self.format_value(field.doc))
        elif isinstance(data_type, Union):
            # Output a union definition.
            self.emit('')
            self.emit('union %s' % data_type.name)
            with self.indent():
                if data_type.doc is not None:
                    self.emit(self.format_string(data_type.doc))
                for field in data_type.fields:
                    name = field.name
                    # Add a star for a catch-all field.
                    # (There are two ways to recognize these.)
                    if field.catch_all or field is data_type.catch_all_field:
                        name += '*'
                    if isinstance(field.data_type, Void):
                        self.emit('%s' % (name))
                    else:
                        type_repr = self.format_data_type(field.data_type)
                        self.emit('%s %s' % (name, type_repr))
                    if field.doc is not None:
                        with self.indent():
                            self.emit(self.format_value(field.doc))
        else:
            # Don't know what this is.
            self.emit('')
            self.emit('# ??? %s' % repr(data_type))