code: private static Highlighter createHighLighterNorth() {
  		return new Highlighter().setShow(true).setShowTooltip(true).setTooltipAlwaysVisible(true)
  				.setKeepTooltipInsideChart(true).setTooltipLocation(TooltipLocations.NORTH)
  				.setTooltipAxes(TooltipAxes.XY_BAR).setShowMarker(true).setBringSeriesToFront(true);
  	}
docs: Creates the high lighter north.
  
  @return the highlighter