private Geometry computeValidPolygon() throws GeometryException {
    Geometry polygon = polygon();
    if (!polygon.isValid()) {
      polygon = GeoUtils.fixPolygon(polygon);
    }
    return polygon;
  }
Returns this feature as a {@link Polygon} or {@link MultiPolygon} in world web mercator coordinates.

@throws GeometryException if an error occurs constructing the geometry, or of this feature should not be
                          interpreted as a line
planetiler-core/src/main/java/com/onthegomap/planetiler/geo/WithGeometry.java