code: public void createShellStreamSet()
      {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.entry(tc, "createShellStreamSet");
  
          StreamSet streamSet = null;
  
          synchronized (streamSets)
          {
              streamSet = new StreamSet(null,
                              targetMEUuid,
                              0,
                              isLink ? StreamSet.Type.LINK_INTERNAL_OUTPUT : StreamSet.Type.INTERNAL_OUTPUT);
              streamSets.put(null, streamSet);
          }
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.exit(tc, "createShellStreamSet", streamSet);
      }
docs: This method will create a StreamSet with null StreamId.