public static <T extends @Nullable Object, 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);
  }

  /**
   * Returns an empty immutable range map.
   *

    }
  }

  @GwtIncompatible
  static <T extends @Nullable Object, K extends Comparable<? super K>, V>
      Collector<T, ?, ImmutableRangeMap<K, V>> toImmutableRangeMap(
          Function<? super T, Range<K>> keyFunction,
          Function<? super T, ? extends V> valueFunction) {
    checkNotNull(keyFunction);
    checkNotNull(valueFunction);
    return Collector.of(

        new ImmutableRangeMap.Builder<Integer, Integer>().put(rangeOne, 1).put(rangeTwo, 6).build();
    CollectorTester.of(
            ImmutableRangeMap.<Range<Integer>, Integer, Integer>toImmutableRangeMap(
                k -> k, k -> k.lowerEndpoint()))
        .expectCollects(rangeMap, rangeOne, rangeTwo);
  }