code: function handleCustomClick (e, d) {
              let [mouseX, mouseY] = getMousePosition(e);
              let dataPoint = isHorizontal ? getNearestDataPoint2(mouseY) : getNearestDataPoint(mouseX);
  
              dispatcher.call('customClick', e, dataPoint, d3Selection.mouse(e));
          }
docs: Click handler, shows data that was clicked and passes to the user
  @private