@Internal
    @Override
    public SplitEnumerator<KafkaPartitionSplit, KafkaSourceEnumState> createEnumerator(
            SplitEnumeratorContext<KafkaPartitionSplit> enumContext) {
        return new KafkaSourceEnumerator(
                subscriber,
                startingOffsetsInitializer,
                stoppingOffsetsInitializer,
                props,
                enumContext,
                boundedness);
    }
Get a kafkaSourceBuilder to build a {@link KafkaSource}.

@return a Kafka source builder.
inlong-sort/sort-flink/sort-flink-v1.15/sort-connectors/kafka/src/main/java/org/apache/inlong/sort/kafka/source/KafkaSource.java