code: public static <T, K extends Comparable<? super K>, V>
        Collector<T, ?, ImmutableRangeMap<K, V>> toImmutableRangeMap(
            Function<? super T, Range<K>> keyFunction,
            Function<? super T, ? extends V> valueFunction) {
      return CollectCollectors.toImmutableRangeMap(keyFunction, valueFunction);
    }
docs: Returns a {@code Collector} that accumulates the input elements into a new {@code
  ImmutableRangeMap}. As in {@link Builder}, overlapping ranges are not permitted.
  
  @since 23.1