private TopicFetcher subscribeSingleTopic() {
        interceptor = Optional.ofNullable(interceptor).orElse(new MsgTimeInterceptor());
        interceptor.configure(topic);
        TopicFetcher fetcher =
                new PulsarSingleTopicFetcher(topic, context, interceptor, deserializer, pulsarClient);
        if (!fetcher.init()) {
            throw new IllegalStateException("init pulsar single topic fetcher failed");
        }
        return fetcher;
    }
Builder of pulsar single topic fetcher.
inlong-sdk/sort-sdk/src/main/java/org/apache/inlong/sdk/sort/fetcher/pulsar/PulsarTopicFetcherBuilderImpl.java