docs: public static double length(@NonNull MultiPolygon multiPolygon,
                                @NonNull @TurfConstants.TurfUnitCriteria String units) {
      double len = 0;
      List<List<List<Point>>> coordinates = multiPolygon.coordinates();
      for (List<List<Point>> coordinate : coordinates) {
        for (List<Point> theCoordinate : coordinate) {
          len += length(theCoordinate, units);
        }
      }
      return len;
    }