VocabularySerializationTestController.php

<?php

namespace Drupal\vocabulary_serialization_test;

use Drupal\taxonomy\VocabularyInterface;
class VocabularySerializationTestController {
    public function vocabularyResponse(VocabularyInterface $taxonomy_vocabulary) {
        $response = new VocabularyResponse('this is the output');
        $response->setVocabulary($taxonomy_vocabulary);
        return $response;
    }

}