gicentre Zoom Pan

I'd like to know how to change the zoomer ZoomPan setting in GICentre library. I've tried the following:

zoomer.setZoomPanDirection(ZOOM_HORIZONTAL_PAN_BOTH);

but I get a syntax error as it interprets ZOOM_HORIZONTAL_PAN_BOTH as a variable whereas as it should be an Enum. I'm not so familiar with Enum's, but I found the documentation here:

gicentre.org/utils/reference/org/gicentre/utils/move/ZoomPan.ZoomPanDirection.html

I think I just need to know the correct syntax.

Here's an example program:

    import org.gicentre.utils.move.*;

    ZoomPan zoomer;

    void setup(){
      size(600,300);
      zoomer = new ZoomPan(this);
    }

    void draw(){
      background(255);
      zoomer.transform();
      zoomer.setZoomPanDirection(ZOOM_HORIZONTAL_PAN_BOTH);
      stroke(50);

      line(100,height/2,500,height/2);

      ellipse(100,100, 50, 50);
    }

Many thanks.