code: public boolean hasStream(SIBUuid12 streamID)
    {
      //note that although it is true that this method is currently
      //equivalent to !isFlushed(streamID), it may not always be true in
      //the future.
      if(streamSet == null) return false;
      return streamID.equals(streamSet.getStreamID());
    }
docs: returns true if a given set of streams exists
  
  @param streamID