@Override
  public SubscriptionPollPayload deserialize(final ByteBuffer buffer) {
    topicNames = ReadWriteIOUtils.readObjectSet(buffer);
    return this;
  }
The set of topic names that need to be polled.
iotdb-client/service-rpc/src/main/java/org/apache/iotdb/rpc/subscription/payload/poll/PollPayload.java