}

  private boolean containsMapping(
      @CheckForNull Object rowKey, @CheckForNull Object columnKey, @CheckForNull Object value) {
    return value != null && value.equals(get(rowKey, columnKey));
  }

  /** Remove a row key / column key / value mapping, if present. */
  private boolean removeMapping(
      @CheckForNull Object rowKey, @CheckForNull Object columnKey, @CheckForNull Object value) {

    @ParametricNullness final K key;
    Collection<V> delegate;
    @CheckForNull final WrappedCollection ancestor;
    @CheckForNull final Collection<V> ancestorDelegate;

    WrappedCollection(
        @ParametricNullness K key,
        Collection<V> delegate,
        @CheckForNull WrappedCollection ancestor) {
      this.key = key;
      this.delegate = delegate;

  }

  private boolean containsMapping(
      @CheckForNull Object rowKey, @CheckForNull Object columnKey, @CheckForNull Object value) {
    return value != null && value.equals(get(rowKey, columnKey));
  }

  /** Remove a row key / column key / value mapping, if present. */
  private boolean removeMapping(
      @CheckForNull Object rowKey, @CheckForNull Object columnKey, @CheckForNull Object value) {

   * not have been inserted consecutively.
   */
  @CheckForNull private final List<NodeConnection<N>> orderedNodeConnections;

  private int predecessorCount;
  private int successorCount;

  private DirectedGraphConnections(
      Map<N, Object> adjacentNodeValues,
      @CheckForNull List<NodeConnection<N>> orderedNodeConnections,
      int predecessorCount,
      int successorCount) {

  @VisibleForTesting @CheckForNull Integer initialCapacity;
  @VisibleForTesting @CheckForNull Long maximumSize;
  @VisibleForTesting @CheckForNull Long maximumWeight;
  @VisibleForTesting @CheckForNull Integer concurrencyLevel;
  @VisibleForTesting @CheckForNull Strength keyStrength;
  @VisibleForTesting @CheckForNull Strength valueStrength;
  @VisibleForTesting @CheckForNull Boolean recordStats;

  @VisibleForTesting @CheckForNull Integer initialCapacity;
  @VisibleForTesting @CheckForNull Long maximumSize;
  @VisibleForTesting @CheckForNull Long maximumWeight;
  @VisibleForTesting @CheckForNull Integer concurrencyLevel;
  @VisibleForTesting @CheckForNull Strength keyStrength;
  @VisibleForTesting @CheckForNull Strength valueStrength;
  @VisibleForTesting @CheckForNull Boolean recordStats;

    this.inverse = inverse;
  }

  // Query Operations (optimizations)

  @Override
  public boolean containsValue(@CheckForNull Object value) {
    return inverse.containsKey(value);
  }

  // Modification Operations

  @CanIgnoreReturnValue
  @Override
  @CheckForNull
  public V put(@ParametricNullness K key, @ParametricNullness V value) {
    return putInBothMaps(key, value, false);
  }

   * 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);
  }

  /**

      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;