return value != null && value.equals(get(rowKey, columnKey));
  }

  /** Remove a row key / column key / value mapping, if present. */
  private boolean removeMapping(
      @Nullable Object rowKey, @Nullable Object columnKey, @Nullable Object value) {
    if (containsMapping(rowKey, columnKey, value)) {
      remove(rowKey, columnKey);
      return true;
    }