code: public GeoPolygon addHole(List<GeoPoint> hole) {
  		Contracts.assertNotNull( hole, "hole" );
  		this.rings.add( hole );
  		return this;
  	}
docs: Adds a new hole to the polygon.
  
  @param hole a hole, must be contained in the exterior ring and must not overlap or
  intersect another hole
  @return this for chaining