public static Geometry createGeometryCollection(List<Geometry> polygonGroup) {
    return JTS_FACTORY.createGeometryCollection(polygonGroup.toArray(Geometry[]::new));
  }
Returns line strings for every inner and outer ring contained in a polygon.

@throws GeometryException if {@code geom} contains anything other than polygons or line strings
planetiler-core/src/main/java/com/onthegomap/planetiler/geo/GeoUtils.java