Sokil\Mongo\Document::defineId PHP Method

    public function defineId($id)
    {
        if (!$id instanceof \MongoId) {
            try {
                $id = new \MongoId($id);
            } catch (\MongoException $e) {
            }
        }
        $this->mergeUnmodified(array('_id' => $id));
        return $this;
    }