code: public function jsonSerialize()
      {
          return array_map(function ($value) {
              if ($value instanceof JsonSerializable) {
                  return $value->jsonSerialize();
              } elseif ($value instanceof JsonableInterface) {
                  return json_decode($value->toJson(), true);
              } elseif ($value instanceof ArrayableInterface) {
                  return $value->toArray();
              } else {
                  return $value;
              }
          }, $this->items);
      }
docs: Convert the object into something JSON serializable.
  
  @return array