presto-hive/src/main/java/io/prestosql/plugin/hive/s3select/PrestoS3ClientFactory.java/PrestoS3ClientFactory/getAwsCredentials
class PrestoS3ClientFactory:    private static Optional<AWSCredentials> getAwsCredentials(Configuration conf)
    {
        String accessKey = conf.get(S3_ACCESS_KEY);
        String secretKey = conf.get(S3_SECRET_KEY);

        if (isNullOrEmpty(accessKey) || isNullOrEmpty(secretKey)) {
            return Optional.empty();
        }
        return Optional.of(new BasicAWSCredentials(accessKey, secretKey));
    }