@Override
    public boolean containsRow(Object rowKey) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.containsRow(rowKey);
    }

    @Override
    public @Nullable V get(Object rowKey, Object columnKey) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.get(rowKey, columnKey);
    }

    @Override
    public @Nullable V put(R rowKey, C columnKey, V value) {

  }

  @Override
  public boolean contains(@Nullable Object rowKey, @Nullable Object columnKey) {
    Map<C, V> row = safeGet(rowMap(), rowKey);
    return row != null && Maps.safeContainsKey(row, columnKey);
  }

  @Override
  public @Nullable V get(@Nullable Object rowKey, @Nullable Object columnKey) {
    Map<C, V> row = safeGet(rowMap(), rowKey);
    return (row == null) ? null : safeGet(row, columnKey);
  }

   */
  @Override
  public SortedMap<C, V> row(R rowKey) {
    return new TreeRow(rowKey);
  }

  private final class TreeRow extends Row implements SortedMap<C, V> {
    final @Nullable C lowerBound;
    final @Nullable C upperBound;

    TreeRow(R rowKey) {
      this(rowKey, null, null);
    }

    TreeRow(R rowKey, @Nullable C lowerBound, @Nullable C upperBound) {
      super(rowKey);

  @Override
  public boolean contains(@Nullable Object rowKey, @Nullable Object columnKey) {
    return delegate().contains(rowKey, columnKey);
  }

  @Override
  public boolean containsColumn(@Nullable Object columnKey) {
    return delegate().containsColumn(columnKey);
  }

  @Override
  public boolean containsRow(@Nullable Object rowKey) {
    return delegate().containsRow(rowKey);
  }

  @Override

    @ParametricNullness private final R rowKey;
    @ParametricNullness private final C columnKey;
    @ParametricNullness private final V value;

    ImmutableCell(
        @ParametricNullness R rowKey,
        @ParametricNullness C columnKey,
        @ParametricNullness V value) {
      this.rowKey = rowKey;
      this.columnKey = columnKey;
      this.value = value;
    }

   *
   * @param rowKey key of row to search for
   * @param columnKey key of column to search for
   */
  boolean contains(
      @CompatibleWith("R") @Nullable Object rowKey,
      @CompatibleWith("C") @Nullable Object columnKey);

  /**
   * Returns {@code true} if the table contains a mapping with the specified row key.
   *
   * @param rowKey key of row to search for
   */

        rowEntry = null;
      }
    }
  }

  @Override
  public Map<C, V> row(R rowKey) {
    return new Row(rowKey);
  }

  class Row extends IteratorBasedAbstractMap<C, V> {
    final R rowKey;

    Row(R rowKey) {
      this.rowKey = checkNotNull(rowKey);
    }

    @Nullable Map<C, V> backingRowMap;

    final void updateBackingRowMapField() {

  @Override
  public boolean contains(@Nullable Object rowKey, @Nullable Object columnKey) {
    return delegate().contains(rowKey, columnKey);
  }

  @Override
  public boolean containsColumn(@Nullable Object columnKey) {
    return delegate().containsColumn(columnKey);
  }

  @Override
  public boolean containsRow(@Nullable Object rowKey) {
    return delegate().containsRow(rowKey);
  }

  @Override

    @ParametricNullness private final R rowKey;
    @ParametricNullness private final C columnKey;
    @ParametricNullness private final V value;

    ImmutableCell(
        @ParametricNullness R rowKey,
        @ParametricNullness C columnKey,
        @ParametricNullness V value) {
      this.rowKey = rowKey;
      this.columnKey = columnKey;
      this.value = value;
    }

  /**
   * {@inheritDoc}
   *
   * @throws NullPointerException if {@code rowKey} is {@code null}
   */
  @Override
  public ImmutableMap<C, V> row(R rowKey) {
    checkNotNull(rowKey, "rowKey");
    return MoreObjects.firstNonNull((ImmutableMap<C, V>) rowMap().get(rowKey), ImmutableMap.of());
  }

  @Override
  public ImmutableSet<R> rowKeySet() {
    return rowMap().keySet();