@Override
    public Collection<TopicFetcher> getAllFetchers() {
        return fetchers.values();
    }
create fetcher (pulsar,tube,kafka)

@param topic {@link InLongTopic}
@return {@link TopicFetcher}
inlong-sdk/sort-sdk/src/main/java/org/apache/inlong/sdk/sort/manager/InlongSingleTopicManager.java