code: private ClientSession newSession() {
      ClientSession session = new ClientSession(clientId, transport.client(), selector, ioContext, connectionStrategy, sessionTimeout,
                                                unstabilityTimeout
      );
  
      // Update the session change listener.
      if (changeListener != null)
        changeListener.close();
      changeListener = session.onStateChange(this::onStateChange);
  
      // Register all event listeners.
      eventListeners.forEach(l -> l.register(session));
      return session;
    }
docs: Creates a new child session.