docs: @Nullable
    public List<LineString> inner() {
      List<List<Point>> coordinates = coordinates();
      if (coordinates.size() <= 1) {
        return new ArrayList(0);
      }
      List<LineString> inner = new ArrayList<>(coordinates.size() - 1);
      for (List<Point> points : coordinates.subList(1, coordinates.size())) {
        inner.add(LineString.fromLngLats(points));
      }
      return inner;
    }