protected function setRequirementsForAttribute($attribute, array $value)
    {
        $parameters = [];

        foreach ($value as $attrValue) {
            $parameters = array_filter(array_merge(
                $parameters,
                self::getParametersInValue($attrValue)
            ));
        }

        if (!empty($parameters)) {
            $this->requirements[$attribute] = $parameters;
        }
    }