@Override
    public String getFetchKey() {
        return topic.getTopicKey();
    }
Topic fetcher that only consumer one topic.
The advantage of single topic fetcher is that it provide much flexible configuration ability to customize the
components such as {@link Deserializer} and {@link Interceptor} for this very topic.
inlong-sdk/sort-sdk/src/main/java/org/apache/inlong/sdk/sort/api/SingleTopicFetcher.java