public static function makeFirstLevelArray($multilevelData)
    {
        $it = new \RecursiveIteratorIterator(new \RecursiveArrayIterator($multilevelData));
        $keyValueArr = [];
        foreach ($it as $k => $v) {

            $decoded = json_decode($v);
            if (!$decoded || is_int($decoded)) {
                throw new JsonException('Not json.');
            }

            if (is_array($decoded) || is_object($decoded)) {
                $nestedIt = new \RecursiveIteratorIterator(new \RecursiveArrayIterator($decoded));
                foreach ($nestedIt as $nK => $nV) {
                    $keyValueArr[$nK] = $nV;
                }

                continue;
            }

            $keyValueArr[$k] = $v;
        }

        return $keyValueArr;
    }