protected function validateAlpha($value, string $parameter, array $args = [], array $rules = null, array $context = null): ?string
    {
        //$value = $this->getValue($parameter);

        if ($value === null) {
            return null;
        }

        if (!is_scalar($value)) {
            return Message::getMessage(Message::PRIMITIVE, [
                'param' => $parameter
            ]);
        }

        $value = trim((string)$value);

        if ($value === '') {
            return null;
        }

        if (!ctype_alpha($value)) {
            return Message::getMessage(Message::ALPHA, [
                'param' => $parameter,
                'value' => $value
            ]);
        }

        return null;
    }