code: @Override
    public void appendPlotCommands(PlotBundle.Builder sb) {
      sb.append("set grid ");
      sb.append(yesNo(showXMajor)).append("xtics ");
      sb.append(yesNo(showXMinor)).append("mxtics ");
      sb.append(yesNo(showYMajor)).append("ytics ");
      sb.append(yesNo(showYMinor)).append("mytics ");
  
      sb.append(zIndex.asPlotCommand()).append(" ");
      majorLineStyle.appendPlotCommands(sb);
      sb.append(" , ");
      minorLineStyle.appendPlotCommands(sb);
      sb.append(" \nshow grid\n");
    }
docs: /*    set grid {{no}{m}xtics} {{no}{m}ytics} {{no}{m}ztics}
  {{no}{m}x2tics} {{no}{m}y2tics}
  {{no}{m}cbtics}
  {polar {<angle>}}
  {layerdefault | front | back}
  { {linestyle <major_linestyle>}
  | {linetype | lt <major_linetype>}
  {linewidth | lw <major_linewidth>}
  { , {linestyle | ls <minor_linestyle>}
  | {linetype | lt <minor_linetype>}
  {linewidth | lw <minor_linewidth>} } }
  unset grid
  show grid