Use is_iterable() function when possible

Author: javiereguiluz

Serializer.php

@@ -157,7 +157,7 @@ public function normalize($data, $format = null, array $context = [])
             return $data;
         }
 
-        if (\is_array($data) || $data instanceof \Traversable) {
+        if (is_iterable($data)) {
             if (($context[AbstractObjectNormalizer::PRESERVE_EMPTY_OBJECTS] ?? false) === true && $data instanceof \Countable && 0 === $data->count()) {
                 return $data;
             }