private function loadSerializer($config, ContainerBuilder $container)
    {
        $container->setAlias('fos_elastica.serializer', $config['serializer']);

        $serializer = $container->getDefinition('fos_elastica.serializer_callback_prototype');
        $serializer->setClass($config['callback_class']);

        if (is_subclass_of($config['callback_class'], ContainerAwareInterface::class)) {
            $serializer->addMethodCall('setContainer', [new Reference('service_container')]);
        }
    }