public KafkaSourceBuilder<OUT> setKafkaSubscriber(KafkaSubscriber kafkaSubscriber) {
        ensureSubscriberIsNull("custom");
        this.subscriber = checkNotNull(kafkaSubscriber);
        return this;
    }
Set a custom Kafka subscriber to use to discover new splits.

@param kafkaSubscriber the {@link KafkaSubscriber} to use for split discovery.
@return this KafkaSourceBuilder.
inlong-sort/sort-flink/sort-flink-v1.18/sort-connectors/kafka/src/main/java/org/apache/inlong/sort/kafka/source/KafkaSourceBuilder.java