docs: private void checkClosed() throws SIIncorrectCallException
     {
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.entry(tc, "checkClosed", ""+closed);
        if (closed) 
           throw new SIIncorrectCallException(
              TraceNLS.getFormattedMessage(CommsConstants.MSG_BUNDLE, "PROXY_QUEUE_CONVERSATION_GROUP_CLOSED_SICO1059", null, "PROXY_QUEUE_CONVERSATION_GROUP_CLOSED_SICO1059") // D270373
           );
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(tc, "checkClosed");
     }