}
      return this;
    }

    ImmutableTable<R, C, V> toTable() {
      return ImmutableTable.copyOf(insertionOrder);
    }
  }

  @IgnoreJRERequirement // see enclosing class (whose annotation Animal Sniffer ignores here...)
  private static final class MutableCell<R, C, V> extends AbstractCell<R, C, V> {
    private final R row;
    private final C column;
    private V value;