presto-kafka/src/main/java/io/prestosql/plugin/kafka/KafkaTopicFieldGroup.java/KafkaTopicFieldGroup/KafkaTopicFieldGroup
class KafkaTopicFieldGroup:    @JsonCreator
    public KafkaTopicFieldGroup(
            @JsonProperty("dataFormat") String dataFormat,
            @JsonProperty("dataSchema") Optional<String> dataSchema,
            @JsonProperty("fields") List<KafkaTopicFieldDescription> fields)
    {
        this.dataFormat = requireNonNull(dataFormat, "dataFormat is null");
        this.dataSchema = requireNonNull(dataSchema, "dataSchema is null");
        this.fields = ImmutableList.copyOf(requireNonNull(fields, "fields is null"));
    }