* #intersection(Multiset, Multiset) intersection} {@code (multisetToModify, multisetToRetain)},
   * but mutates {@code multisetToModify} instead of returning a view.
   *
   * <p>In contrast, {@code multisetToModify.retainAll(multisetToRetain)} keeps all occurrences of
   * elements that appear at all in {@code multisetToRetain}, and deletes all occurrences of all
   * other elements.
   *

     * platforms we target.
     *
     * 2. Kotlin's Map type has a getOrDefault method that accepts and returns a "plain V," in
     * contrast to the "V?" type that we're using. As a result, Kotlin sees a conflict between the
     * nullness annotations in ImmutableMap and those in its own Map type. In response, it considers

    return transformEntries(fromMultimap, transformer);
  }

  /**
   * Returns a view of a multimap whose values are derived from the original multimap's entries. In
   * contrast to {@link #transformValues}, this method's entry-transformation logic may depend on
   * the key as well as the value.
   *
   * <p>All other properties of the transformed multimap, such as iteration order, are left intact.

    return transformEntries(fromMap, asEntryTransformer(function));
  }

  /**
   * Returns a view of a map whose values are derived from the original map's entries. In contrast
   * to {@link #transformValues}, this method's entry-transformation logic may depend on the key as
   * well as the value.
   *

         configurations downstream, and GWT uses the runtime configuration for
         its builds. Thus, GWT doesn't get j2objc-annotations transitively, in
         contrast to the other deps of `guava`, which it does get transitively.
         (Arguably we should redeclare *all* the `guava` deps here.) -->
    <dependency>
      <groupId>com.google.j2objc</groupId>

   */
  public static <T extends @Nullable Object> Iterator<T> concat(
      Iterator<? extends Iterator<? extends T>> inputs) {
    return new ConcatenatedIterator<>(inputs);
  }

  /** Concats a varargs array of iterators without making a defensive copy of the array. */
  static <T extends @Nullable Object> Iterator<T> concatNoDefensiveCopy(
      Iterator<? extends T>... inputs) {