code: public OPTICSPlot getOPTICSPlot(VisualizerContext context) {
      if(plot == null) {
        plot = OPTICSPlot.plotForClusterOrder(clusterOrder, context);
      }
      return plot;
    }
docs: Get or produce the actual OPTICS plot.
  
  @param context Context to use
  @return Plot