public function getVersionSteps()
    {
        if ($this->_versionSteps === null) {
            $currentVersion = Yii::$app->session->get(self::SESSION_VERSION, 0);
            $versionSteps = [];
            foreach ($this->steps as $version => $steps) {
                if (Helper::compareVersions(explode('.', $currentVersion), explode('.', $version)) == '<') {
                    $versionSteps += $steps;
                }
            }
            $this->_versionSteps = $versionSteps;
        }
        return $this->_versionSteps;
    }