Function<? super T, ? extends K> keyFunction,
          Function<? super T, ? extends V> valueFunction) {
    checkNotNull(keyFunction, "keyFunction");
    checkNotNull(valueFunction, "valueFunction");
    return Collector.of(
        ImmutableListMultimap::<K, V>builder,
        (builder, t) -> builder.put(keyFunction.apply(t), valueFunction.apply(t)),
        ImmutableListMultimap.Builder::combine,

   * stream.collect(ImmutableMap.toImmutableMap(keyFunction, v -> v))}.
   *
   * @param keyFunction the function used to produce the key for each value
   * @return a map mapping the result of evaluating the function {@code keyFunction} on each value
   *     in this fluent iterable to that value
   * @throws IllegalArgumentException if {@code keyFunction} produces the same key for more than one

          Function<? super T, ? extends K> keyFunction,
          Function<? super T, ? extends V> valueFunction,
          BinaryOperator<V> mergeFunction) {
    checkNotNull(comparator);
    checkNotNull(keyFunction);
    checkNotNull(valueFunction);
    checkNotNull(mergeFunction);
    return Collectors.collectingAndThen(
        Collectors.toMap(

  public static <T extends @Nullable Object, K, V>
      Collector<T, ?, ImmutableBiMap<K, V>> toImmutableBiMap(
          Function<? super T, ? extends K> keyFunction,
          Function<? super T, ? extends V> valueFunction) {
    return CollectCollectors.toImmutableBiMap(keyFunction, valueFunction);
  }

  // Casting to any type is safe because the set will never hold any elements.
  @SuppressWarnings("unchecked")

   *
   * @param values the values to use when constructing the {@code Map}
   * @param keyFunction the function used to produce the key for each value
   * @return a map mapping the result of evaluating the function {@code keyFunction} on each value
   *     in the input collection to that value
   * @throws IllegalArgumentException if {@code keyFunction} produces the same key for more than one
   *     value in the input collection

   *
   * @param values the values to use when constructing the {@code Map}
   * @param keyFunction the function used to produce the key for each value
   * @return a map mapping the result of evaluating the function {@code keyFunction} on each value
   *     in the input collection to that value
   * @throws IllegalArgumentException if {@code keyFunction} produces the same key for more than one
   *     value in the input collection

  public static <T extends @Nullable Object, K, V>
      Collector<T, ?, ImmutableBiMap<K, V>> toImmutableBiMap(
          Function<? super T, ? extends K> keyFunction,
          Function<? super T, ? extends V> valueFunction) {
    return CollectCollectors.toImmutableBiMap(keyFunction, valueFunction);
  }

  /**
   * Returns the empty bimap.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */

   * @param keyFunction the function used to produce the key for each value
   * @return {@code ImmutableListMultimap} mapping the result of evaluating the function {@code
   *     keyFunction} on each value in the input collection to that value
   * @throws NullPointerException if any element of {@code values} is {@code null}, or if {@code
   *     keyFunction} produces {@code null} for any key
   */

      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.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.

   */
  public static <T extends @Nullable Object, K, V>
      Collector<T, ?, ImmutableBiMap<K, V>> toImmutableBiMap(
          Function<? super T, ? extends K> keyFunction,
          Function<? super T, ? extends V> valueFunction) {
    return CollectCollectors.toImmutableBiMap(keyFunction, valueFunction);
  }

  /**
   * Returns the empty bimap.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */