Can't make anyType to work with soap-client about soap-client HOT 1 OPEN

class SerializerMixedSubscribingHandler implements SubscribingHandlerInterface

{
    public static function getSubscribingMethods()
    {
        return array(
            array(
                'direction' => GraphNavigatorInterface::DIRECTION_DESERIALIZATION,
                'format' => 'xml',
                'type' => 'mixed',
                'method' => 'deserializeMixedType'
            ),
            array(
                'direction' => GraphNavigatorInterface::DIRECTION_SERIALIZATION,
                'format' => 'xml',
                'type' => 'mixed',
                'method' => 'serializeMixedType'
            )
        );
    }

    public function serializeMixedType(XmlSerializationVisitor $visitor, $data, array $type, Context $context)
    {
        return $visitor->visitSimpleString(strval($data), $type);
    }

    public function deserializeMixedType(XmlDeserializationVisitor $visitor, $data, array $type)
    {
        return strval($visitor->getResult($data));
    }
}

        $serializer = SoapContainerBuilder::createSerializerBuilderFromContainer($container, function ($handler) {
            /** @var HandlerRegistryInterface $handler */
            $handler->registerSubscribingHandler(new SerializerMixedSubscribingHandler());
        }, $projectDir)
            ->build();