extends IteratorBasedAbstractMap<K, V> implements NavigableMap<K, V> {

  @Override
  @CheckForNull
  public abstract V get(@CheckForNull Object key);

  @Override
  @CheckForNull
  public Entry<K, V> firstEntry() {
    return Iterators.<@Nullable Entry<K, V>>getNext(entryIterator(), null);
  }

  @Override
  @CheckForNull
  public Entry<K, V> lastEntry() {

  }

  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) {

  @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) {

    extends IteratorBasedAbstractMap<K, V> implements NavigableMap<K, V> {

  @Override
  @CheckForNull
  public abstract V get(@CheckForNull Object key);

  @Override
  @CheckForNull
  public Entry<K, V> firstEntry() {
    return Iterators.<@Nullable Entry<K, V>>getNext(entryIterator(), null);
  }

  @Override
  @CheckForNull
  public Entry<K, V> lastEntry() {

  @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;

    return delegate().offerLast(e);
  }

  @Override
  @CheckForNull
  public E peekFirst() {
    return delegate().peekFirst();
  }

  @Override
  @CheckForNull
  public E peekLast() {
    return delegate().peekLast();
  }

  @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
  @Override
  @CheckForNull
  public E pollFirst() {
    return delegate().pollFirst();
  }

  public VerifyException(@CheckForNull String message) {
    super(message);
  }

  /**
   * Constructs a {@code VerifyException} with the cause {@code cause} and a message that is {@code
   * null} if {@code cause} is null, and {@code cause.toString()} otherwise.
   *
   * @since 19.0
   */
  public VerifyException(@CheckForNull Throwable cause) {
    super(cause);
  }

  /**

    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);
  }