docs: public long generateMailboxId(Long mailboxId) {
          final long hsId = mailboxId == null ? getHSIdForLocalSite(m_nextSiteId.getAndIncrement()) : mailboxId;
          addMailbox(hsId, new Mailbox() {
              @Override
              public void send(long hsId, VoltMessage message) {
              }
  
              @Override
              public void send(long[] hsIds, VoltMessage message) {
              }
  
              @Override
              public void deliver(VoltMessage message) {
                  networkLog.info("No-op mailbox(" + CoreUtils.hsIdToString(hsId) + ") dropped message " + message);
              }
  
              @Override
              public void deliverFront(VoltMessage message) {
              }
  
              @Override
              public VoltMessage recv() {
                  return null;
              }
  
              @Override
              public VoltMessage recvBlocking() {
                  return null;
              }
  
              @Override
              public VoltMessage recvBlocking(long timeout) {
                  return null;
              }
  
              @Override
              public VoltMessage recv(Subject[] s) {
                  return null;
              }
  
              @Override
              public VoltMessage recvBlocking(Subject[] s) {
                  return null;
              }
  
              @Override
              public VoltMessage recvBlocking(Subject[] s, long timeout) {
                  return null;
              }
  
              @Override
              public long getHSId() {
                  return 0L;
              }
  
              @Override
              public void setHSId(long hsId) {
              }
  
          });
          return hsId;
      }