Locker\Helpers\Helpers::convertIds PHP Method

    public static function convertIds($models = [])
    {
        return array_map(function ($model) {
            $idString = \MongoId::isValid($model['_id']) ? $model['_id'] : null;
            $model['_id'] = new \MongoId($idString);
            return $model;
        }, $models);
    }

 public function up()
 {
     $db = \DB::getMongoDB();
     Lrs::get()->each(function (Lrs $lrs) use($db) {
         if (isset($lrs->users)) {
             $lrs->users = Helpers::convertIds($lrs->users);
         }
         $lrs->owner_id = new \MongoId($lrs->owner_id);
         $lrs->save();
         echo 'IDs for lrs collection "' . $lrs->title . '" converted to MongoIds.' . PHP_EOL;
     });
 }