BundleConstraintValidator.php

<?php

namespace Drupal\Core\Entity\Plugin\Validation\Constraint;

use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidator;

/**
 * Validates the Bundle constraint.
 */
class BundleConstraintValidator extends ConstraintValidator {
    
    /**
     * {@inheritdoc}
     */
    public function validate($entity, Constraint $constraint) {
        if (!isset($entity)) {
            return;
        }
        if (!in_array($entity->bundle(), $constraint->getBundleOption())) {
            $this->context
                ->addViolation($constraint->message, [
                '%bundle' => implode(', ', $constraint->getBundleOption()),
            ]);
        }
    }

}