return false;
    }
    for (Map<C, V> map : backingMap.values()) {
      if (safeContainsKey(map, columnKey)) {
        return true;
      }
    }
    return false;
  }

  @Override
  public boolean containsRow(@Nullable Object rowKey) {
    return rowKey != null && safeContainsKey(backingMap, rowKey);
  }

  @Override
  public boolean containsValue(@Nullable Object value) {

    implements Table<R, C, V> {

  @Override
  public boolean containsRow(@Nullable Object rowKey) {
    return Maps.safeContainsKey(rowMap(), rowKey);
  }

  @Override
  public boolean containsColumn(@Nullable Object columnKey) {
    return Maps.safeContainsKey(columnMap(), columnKey);
  }

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

  @Override

      return null;
    }
  }

  /**
   * Delegates to {@link Map#containsKey}. Returns {@code false} on {@code ClassCastException} and
   * {@code NullPointerException}.
   */
  static boolean safeContainsKey(Map<?, ?> map, @Nullable Object key) {
    checkNotNull(map);
    try {
      return map.containsKey(key);
    } catch (ClassCastException | NullPointerException e) {
      return false;
    }
  }

      return null;
    }
  }

  /**
   * Delegates to {@link Map#containsKey}. Returns {@code false} on {@code ClassCastException} and
   * {@code NullPointerException}.
   */
  static boolean safeContainsKey(Map<?, ?> map, @Nullable Object key) {
    checkNotNull(map);
    try {
      return map.containsKey(key);
    } catch (ClassCastException | NullPointerException e) {
      return false;
    }
  }