public boolean isEmpty() {
    return size() == 0;
  }

  @Override
  public boolean containsKey(@Nullable Object key) {
    return get(key) != null;
  }

  @Override
  public boolean containsValue(@Nullable Object value) {
    return values().contains(value);
  }

  private transient @Nullable ImmutableSet<Entry<K, V>> cachedEntrySet = null;

  public final ImmutableSet<Entry<K, V>> entrySet() {

    @CheckForNull Comparator<? super V> valueComparator;
    @Nullable Object[] alternatingKeysAndValues;
    int size;
    boolean entriesUsed;
    /**
     * If non-null, a duplicate key we found in a previous buildKeepingLast() or buildOrThrow()
     * call. A later buildOrThrow() can simply report this duplicate immediately.
     */
    @Nullable DuplicateKey duplicateKey;

    /**

   */
  @Deprecated
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  @CheckForNull
  public final V compute(
      K key, BiFunction<? super K, ? super @Nullable V, ? extends @Nullable V> remappingFunction) {
    throw new UnsupportedOperationException();
  }

  /**
   * Guaranteed to throw an exception and leave the map unmodified.
   *