private Feature empty(String layer) {
    return new Feature(layer, EMPTY_GEOM, source.id());
  }
Starts building a new polygon, line, or point map feature based on the geometry type of the input feature.

@param layer the output vector tile layer this feature will be written to
@return a feature that can be configured further.
planetiler-core/src/main/java/com/onthegomap/planetiler/FeatureCollector.java