RainLab\Builder\Classes\MigrationModel::load PHP Method

    public function load($versionNumber)
    {
        $versionNumber = trim($versionNumber);
        if (!strlen($versionNumber)) {
            throw new ApplicationException('Cannot load the the version model - the version number should not be empty.');
        }
        $pluginVersions = $this->getPluginVersionInformation();
        if (!array_key_exists($versionNumber, $pluginVersions)) {
            throw new ApplicationException('The requested version does not exist in the version information file.');
        }
        $this->version = $versionNumber;
        $this->originalVersion = $this->version;
        $this->exists = true;
        $versionInformation = $pluginVersions[$versionNumber];
        if (!is_array($versionInformation)) {
            $this->description = $versionInformation;
        } else {
            $cnt = count($versionInformation);
            if ($cnt > 2) {
                throw new ApplicationException('The requested version cannot be edited with Builder as it refers to multiple PHP scripts.');
            }
            if ($cnt > 0) {
                $this->description = $versionInformation[0];
            }
            if ($cnt > 1) {
                $this->scriptFileName = pathinfo(trim($versionInformation[1]), PATHINFO_FILENAME);
                $this->code = $this->loadScriptFile();
            }
        }
        $this->originalScriptFileName = $this->scriptFileName;
    }

 protected function loadOrCreateBaseModel($versionNumber, $options = [])
 {
     $model = new MigrationModel();
     if (isset($options['pluginCode'])) {
         $model->setPluginCode($options['pluginCode']);
     }
     if (!$versionNumber) {
         return $model;
     }
     $model->load($versionNumber);
     return $model;
 }