Yaml.php

<?php

namespace Drupal\Core\Serialization;

use Drupal\Core\Site\Settings;
use Drupal\Component\Serialization\Yaml as ComponentYaml;

/**
 * Provides a YAML serialization implementation.
 *
 * Allow settings to override the YAML implementation resolution.
 */
class Yaml extends ComponentYaml {
    
    /**
     * {@inheritdoc}
     */
    protected static function getSerializer() {
        // Allow settings.php to override the YAML serializer.
        if (!isset(static::$serializer) && ($class = Settings::get('yaml_parser_class'))) {
            static::$serializer = $class;
        }
        return parent::getSerializer();
    }

}