public function findEffect($effectIdentifier)
    {
        // find effect model based on the effectIdentifier
        $model = StorageEffect::find()->where(['identifier' => $effectIdentifier])->asArray()->one();
        // if the effect model could not found, throw Exception.
        if (!$model) {
            throw new Exception("The requested effect '$effectIdentifier' does not exist.");
        }
        // array
        return $model;
    }