Add “use” block in BookAttributeNormalizer

Author: alexislefebvre

core/serialization.md

@@ -448,6 +448,11 @@ Here is an example:
 
 namespace App\Serializer;
 
+use Symfony\Component\Security\Core\Authentication\Token\Storage\TokenStorageInterface;
+use Symfony\Component\Serializer\Normalizer\ContextAwareNormalizerInterface;
+use Symfony\Component\Serializer\SerializerAwareInterface;
+use Symfony\Component\Serializer\SerializerAwareTrait;
+
 class BookAttributeNormalizer implements ContextAwareNormalizerInterface, SerializerAwareInterface
 {
     use SerializerAwareTrait;