* wish to override {@link #lower} to forward to this implementation.
   */
  @CheckForNull
  protected E standardLower(@ParametricNullness E e) {
    return Iterators.getNext(headSet(e, false).descendingIterator(), null);
  }

  @Override
  @CheckForNull
  public E floor(@ParametricNullness E e) {
    return delegate().floor(e);
  }

  /**

  @CanIgnoreReturnValue
  @Override
  @CheckForNull
  public V remove(@CheckForNull Object rowKey, @CheckForNull Object columnKey) {
    Map<C, V> row = Maps.safeGet(rowMap(), rowKey);
    return (row == null) ? null : Maps.safeRemove(row, columnKey);
  }

  @CanIgnoreReturnValue
  @Override
  @CheckForNull
  public V put(
      @ParametricNullness R rowKey, @ParametricNullness C columnKey, @ParametricNullness V value) {

   * lowerEntry} to forward to this implementation.
   */
  @CheckForNull
  protected Entry<K, V> standardLowerEntry(@ParametricNullness K key) {
    return headMap(key, false).lastEntry();
  }

  @Override
  @CheckForNull
  public K lowerKey(@ParametricNullness K key) {
    return delegate().lowerKey(key);
  }

  /**

   * lowerEntry} to forward to this implementation.
   */
  @CheckForNull
  protected Entry<K, V> standardLowerEntry(@ParametricNullness K key) {
    return headMap(key, false).lastEntry();
  }

  @Override
  @CheckForNull
  public K lowerKey(@ParametricNullness K key) {
    return delegate().lowerKey(key);
  }

  /**

    return delegate().containsValue(value);
  }

  @Override
  @CheckForNull
  public V get(@CheckForNull Object rowKey, @CheckForNull Object columnKey) {
    return delegate().get(rowKey, columnKey);
  }

  @Override
  public boolean isEmpty() {
    return delegate().isEmpty();
  }

  @CanIgnoreReturnValue
  @Override
  @CheckForNull
  public V put(

      OutSpliteratorT newFlatMapSpliterator(
          @CheckForNull OutSpliteratorT prefix,
          Spliterator<InElementT> fromSplit,
          Function<? super InElementT, @Nullable OutSpliteratorT> function,
          int splitCharacteristics,
          long estSplitSize);
    }

    @Weak @CheckForNull OutSpliteratorT prefix;
    final Spliterator<InElementT> from;

   *
   * @since 19.0
   */
  public static <K, V> RemovalNotification<K, V> create(
      @CheckForNull K key, @CheckForNull V value, RemovalCause cause) {
    return new RemovalNotification<>(key, value, cause);
  }

  private RemovalNotification(@CheckForNull K key, @CheckForNull V value, RemovalCause cause) {
    super(key, value);
    this.cause = checkNotNull(cause);
  }

     * 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) {
      super(key, value);
      this.nextInKeyBucket = nextInKeyBucket;
    }

    @Override
    @CheckForNull
    final ImmutableMapEntry<K, V> getNextInKeyBucket() {

  }

  @Override
  @CheckForNull
  public V edgeValueOrDefault(N nodeU, N nodeV, @CheckForNull V defaultValue) {
    return edgeValueOrDefaultInternal(checkNotNull(nodeU), checkNotNull(nodeV), defaultValue);
  }

  @Override
  @CheckForNull
  public V edgeValueOrDefault(EndpointPair<N> endpoints, @CheckForNull V defaultValue) {
    validateEndpoints(endpoints);

  @Override
  public Comparator<? super E> comparator() {
    return comparator;
  }

  @Override
  @CheckForNull
  public Entry<E> firstEntry() {
    Iterator<Entry<E>> entryIterator = entryIterator();
    return entryIterator.hasNext() ? entryIterator.next() : null;
  }

  @Override
  @CheckForNull
  public Entry<E> lastEntry() {
    Iterator<Entry<E>> entryIterator = descendingEntryIterator();