docs: @Override
      public org.apache.lucene.search.SortField sortField(Schema schema) {
          final Mapper mapper = schema.mapper(field);
          if (mapper == null) {
              throw new IndexException("Field '{}' is not found", field);
          } else if (!(mapper instanceof GeoPointMapper)) {
              throw new IndexException("Field '{}' type is not geo_point", field);
          }
          GeoPointMapper geoPointMapper = (GeoPointMapper) mapper;
  
          Point point = CONTEXT.makePoint(longitude, latitude);
  
          // Use the distance (in km) as source
          SpatialStrategy strategy = geoPointMapper.strategy.getGeometryStrategy();
          ValueSource valueSource = strategy.makeDistanceValueSource(point, DistanceUtils.DEG_TO_KM);
          return valueSource.getSortField(reverse);
      }