Symfony serializer groups

Code
<?php

use Symfony\Component\Serializer\Serializer;
use Symfony\Component\Serializer\Encoder\XmlEncoder;
use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;

use Symfony\Component\Serializer\Mapping\Loader\AnnotationLoader;
use Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactory;
use Doctrine\Common\Annotations\AnnotationReader;
use Symfony\Component\Serializer\Annotation\Groups;

$xmlEncoder = new XmlEncoder();

// Enable annotations for serializer
$classMetadataFactory = new ClassMetadataFactory(
    new AnnotationLoader(new AnnotationReader())
);
$normalizer = new ObjectNormalizer($classMetadataFactory);

$serializer = new Serializer([$normalizer], [$xmlEncoder]);

$object = new class() {

    public $foo = 1;
    
    /**
     * @Groups({"text_only"})
     */
    public $bar = 'text';
    
    public $qux;
};

$serialized = $serializer->encode($object, 'xml');
echo htmlentities($serialized) . PHP_EOL;

$serialized = $serializer->encode($object, 'xml', ['groups' => ['text_only']]);
echo htmlentities($serialized);
Result
<?xml version="1.0"?>
<response><foo>1</foo><bar>text</bar><qux/></response>

<?xml version="1.0"?>
<response><bar>text</bar></response>