docs: private void checkValid() throws SISessionUnavailableException
     {
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.entry(this, tc,"checkValid");
        
        // Start f
        if (invalid ||                                     // If the callback has finished
            consumerSession.isClosed() ||                  // If the parent session is closed
            (Thread.currentThread() != owningThread))      // If we are on a different thread
        {
           if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) SibTr.debug(this, tc,"not valid", this);
           invalid = true;
           throw new SISessionUnavailableException(null);
        }
        // End f
        
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(this, tc,"checkValid");
     }