rf3main/frontend/modules/open/Module.php

<?php

namespace frontend\modules\open;

/**
 * open module definition class
 */
class Module extends \yii\base\Module
{
    /**
     * {@inheritdoc}
     */
    public $controllerNamespace = 'frontend\modules\open\controllers';

    /**
     * {@inheritdoc}
     */
    public function init()
    {
        parent::init();

        // custom initialization code goes here
    }
}