public function save()
    {
        if ($this->root !== $this) {
            return $this->root->save();
        }
        if (! isset($this->store)) {
            return false;
        }
        if (! $this->updated) {
            return true;
        }
        $this->store->open(true);
        $this->store->write($this->data);
        $this->store->close();
        $this->updated = false;
        return true;
    }