protected function _validateScope(AnConfig $config)
    {
        $property = $config->property;
        $value = $config->value;
        $entity = $config->entity;
        $options = AnConfig::unbox($config->options);

        if (!in_array($value, $options)) {
            $entity->addError(array(
                'message' => $property->getName().' must be one of the value of '.implode($options, ','),
                'code' => AnError::OUT_OF_SCOPE,
                'key' => $property->getName(),
                'scope' => $options,
            ));

            return false;
        }

        return true;
    }