public static <K, V> MergingRangeMap<Map<K, V>> unitMap() {
    return unit(Map.of(), MapUtil::merge);
  }
Returns a new range map where values are {@link Map Maps} that get merged together when they overlap from
{@code [0, 1)}.
planetiler-core/src/main/java/com/onthegomap/planetiler/util/MergingRangeMap.java