public function createCredentials(Result $result)
    {
        if (!$result->hasKey('Credentials')) {
            throw new \InvalidArgumentException('Result contains no credentials');
        }

        $c = $result['Credentials'];

        return new Credentials(
            $c['AccessKeyId'],
            $c['SecretAccessKey'],
            isset($c['SessionToken']) ? $c['SessionToken'] : null,
            isset($c['Expiration']) && $c['Expiration'] instanceof \DateTimeInterface
                ? (int) $c['Expiration']->format('U')
                : null
        );
    }