protected function processNestedArray($parentIdentifier, array $nestedArray, \Closure $handler = null)
    {
        $identifier = 'a' . Algorithms::generateRandomString(23);
        $data = [
            'multivalue' => true,
            'value' => $this->processArray($nestedArray, $parentIdentifier)
        ];
        if ($handler instanceof \Closure) {
            $handler($parentIdentifier, $identifier, $data);
        }
        return $identifier;
    }