@Override
  protected Geometry transformPolygon(Polygon geom, Geometry parent) {
    return geom.isEmpty() ? null : super.transformPolygon(geom, parent);
  }
Returns the square of the number of units that (px, p1) is away from the line segment from (p1x, py1) to (p2x,
p2y).
planetiler-core/src/main/java/com/onthegomap/planetiler/geo/DouglasPeuckerSimplifier.java