public KafkaSource<OUT> build() {
        sanityCheck();
        parseAndSetRequiredProperties();
        return new KafkaSource<>(
                subscriber,
                startingOffsetsInitializer,
                stoppingOffsetsInitializer,
                boundedness,
                deserializationSchema,
                props,
                rackIdSupplier);
    }
Build the {@link KafkaSource}.

@return a KafkaSource with the settings made for this builder.
inlong-sort/sort-flink/sort-flink-v1.18/sort-connectors/kafka/src/main/java/org/apache/inlong/sort/kafka/source/KafkaSourceBuilder.java