protected function normalizeAsArray($objects) : array
    {
        $key = $this->relation;

        if (!is_array($objects) && !$objects instanceof Collection) {
            throw new MappingException("column '$key' should be of type array or collection");
        }

        if ($objects instanceof Collection) {
            $objects = $objects->all();
        }

        $normalizedObjects = [];

        foreach ($objects as $object) {
            $wrapper = $this->factory->make($object);
            $normalizedObjects[] = $wrapper->getEntityAttributes();
        }

        if ($this->asJson) {
            $normalizedObjects = json_encode($normalizedObjects);
        }

        return [$key => $normalizedObjects];
    }