code: public static Bbox buffer(Bbox bbox, double range) {
  		if (range >= 0) {
  			double r2 = range * 2;
  			return new Bbox(bbox.getX() - range, bbox.getY() - range, bbox.getWidth() + r2, bbox.getHeight() + r2);
  		}
  		throw new IllegalArgumentException("Buffer range must always be positive.");
  	}
docs: Return a new bounding box that has increased in size by adding a range to a given bounding box.
  
  @param bbox
  The original bounding box to calculate a buffer for. This one will remain untouched.
  @param range
  Must be a positive number, otherwise null will be returned.
  @return The result as a new bounding box.