code: public void attachMessage(ConsumableKey consumerKey)
    {
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
      {
        SibTr.entry(tc, "attachMessage", msgAttachedMember);
        SibTr.exit(tc, "attachMessage", consumerKey);
      }
      if(msgAttachedMember == null)
        msgAttachedMember = consumerKey;
      else
      {
        // We already have a message attached
        if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) SibTr.exit(tc, "attachMessage", "SIErrorException");
          throw new SIErrorException(
            nls.getFormattedMessage(
              "INTERNAL_MESSAGING_ERROR_CWSIP0001",
              new Object[] {
                "com.ibm.ws.sib.processor.impl.LocalQPConsumerKeyGroup",
                "1:1027:1.6.1.14" },
              null));
      }
    }
docs: Record the fact that one of the members has a message attached
  @param consumerKey