private function _getRoots()
{
$directories = [];
if (is_string($this->module->root)) {
$root = Yii::getAlias($this->module->root);
if ($this->module->scanRootParentDirectory) {
$root = dirname($root);
}
$directories[] = $root;
} elseif (is_array($this->module->root)) {
foreach ($this->module->root as $root) {
$directories[] = Yii::getAlias($root);
}
} else {
throw new InvalidConfigException("Invalid `root` option value!");
}
return $directories;
}