@Override
  public boolean equals(final Object obj) {
    if (this == obj) {
      return true;
    }
    if (obj == null || getClass() != obj.getClass()) {
      return false;
    }
    final ConsumerGroupMeta that = (ConsumerGroupMeta) obj;
    return Objects.equals(this.consumerGroupId, that.consumerGroupId)
        && this.creationTime == that.creationTime
        && Objects.equals(
            this.topicNameToSubscribedConsumerIdSet, that.topicNameToSubscribedConsumerIdSet)
        && Objects.equals(this.consumerIdToConsumerMeta, that.consumerIdToConsumerMeta)
        && Objects.equals(
            this.topicNameToSubscriptionCreationTime, that.topicNameToSubscriptionCreationTime);
  }
@return topics subscribed by no consumers in this group after this removal.
@param consumerId if null, remove subscriptions of topics for all consumers
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/subscription/meta/consumer/ConsumerGroupMeta.java