* <i>adding</i> to the returned set is not possible.
   */
  @Override
  public Set<K> keySet() {
    return super.keySet();
  }

  /**
   * Returns a collection of all values in the multimap. Changes to the returned collection will
   * update the underlying multimap, and vice versa.
   *

  /*
   * We have some considerable complexity in these create methods because of
   * Builder.buildKeepingLast(). The same Builder might be called with buildKeepingLast() and then
   * buildOrThrow(), or vice versa. So in particular, if we modify alternatingKeysAndValues to
   * eliminate duplicate keys (for buildKeepingLast()) then we have to ensure that a later call to

      Sets.newSetFromMap(map);
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  /** The 0-ary cartesian product is a single empty list. */
  public void testCartesianProduct_zeroary() {
    assertThat(Sets.cartesianProduct()).containsExactly(list());
  }

  /** A unary cartesian product is one list of size 1 for each element in the input set. */
  public void testCartesianProduct_unary() {

  /**
   * Returns a view of the complement of this {@code RangeSet}.
   *
   * <p>The returned view supports the {@link #add} operation if this {@code RangeSet} supports
   * {@link #remove}, and vice versa.
   */
  RangeSet<C> complement();

  /**
   * Returns a view of the intersection of this {@code RangeSet} with the specified range.
   *

   * Returns a list that applies {@code function} to each element of {@code fromList}. The returned
   * list is a transformed view of {@code fromList}; changes to {@code fromList} will be reflected
   * in the returned list and vice versa.
   *
   * <p>Since functions are not reversible, the transform is one-way and new items cannot be stored
   * in the returned list. The {@code add}, {@code addAll} and {@code set} methods are unsupported

     * use `get(key) ?: defaultValue` instead of this method, anyway.
     */
    V result = get(key);
    // TODO(b/192579700): Use a ternary once it no longer confuses our nullness checker.
    if (result != null) {
      return result;
    } else {
      return defaultValue;
    }
  }

       *
       * (And I don't believe there's any situation in which we call x.combine(y) when x is a plain
       * ImmutableSet.Builder but y is an ImmutableSortedSet.Builder (or vice versa). Certainly
       * ImmutableSortedSet.Builder.combine() is written as if its argument will never be a plain
       * ImmutableSet.Builder: It casts immediately to ImmutableSortedSet.Builder.)
       */

      if (leftChildIndex < 0) {
        return -1;
      }
      return findMin(getLeftChildIndex(leftChildIndex), 4);
    }

    /**
     * Moves an element one level up from a min level to a max level (or vice versa). Returns the
     * new position of the element.
     */
    int crossOverUp(int index, E x) {
      if (index == 0) {
        queue[0] = x;
        return 0;
      }

     * do that with a plain NonTerminalImmutableMapEntry, but we do it with the BiMap-specific
     * subclass below. That's because the Entry might be non-terminal in the key bucket but terminal
     * in the value bucket (or vice versa).
     */
    @CheckForNull private final transient ImmutableMapEntry<K, V> nextInKeyBucket;

    NonTerminalImmutableMapEntry(
        K key, V value, @CheckForNull ImmutableMapEntry<K, V> nextInKeyBucket) {

   * the table lacks a mapping for a given row and column, the corresponding array element is null.
   *
   * <p>Subsequent table changes will not modify the array, and vice versa.
   *
   * @param valueClass class of values stored in the returned array
   */
  @GwtIncompatible // reflection
  public @Nullable V[][] toArray(Class<V> valueClass) {