public Set<String> getConsumersSubscribingTopic(final String topic) {
    return topicNameToSubscribedConsumerIdSet.getOrDefault(topic, Collections.emptySet());
  }
Get the consumers subscribing the given topic in this group.

@param topic The topic name.
@return The set of consumer IDs subscribing the given topic in this group. If no consumer is
    subscribing the topic, return an empty set.
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/subscription/meta/consumer/ConsumerGroupMeta.java