reducer

An expression that aggregates values produced by the mapper. The special function org.maplibre.compose.expressions.dsl.Feature.accumulated will return the value accumulated so far, and the feature property with the name of the property will return the next value to aggregate.

Example:

GeoJsonOptions.ClusterPropertyAggregator(
  mapper = feature["current_range_meters"].asNumber(),
  reducer = feature["total_range"].asNumber() + feature.accumulated().asNumber(),
)