presto-kafka/src/main/java/io/prestosql/plugin/kafka/KafkaTopicFieldGroup.java/KafkaTopicFieldGroup/toString
class KafkaTopicFieldGroup:    @Override
    public String toString()
    {
        return toStringHelper(this)
                .add("dataFormat", dataFormat)
                .add("dataSchema", dataSchema)
                .add("fields", fields)
                .toString();
    }