}

  @SuppressWarnings("serial") // serialized using ImmutableList serialization
  private static final class StringAsImmutableList extends ImmutableList<Character> {

    private final String string;

    StringAsImmutableList(String string) {
      this.string = string;
    }

    @Override
    public int indexOf(@CheckForNull Object object) {

  }

  @SuppressWarnings("serial") // serialized using ImmutableList serialization
  private static final class StringAsImmutableList extends ImmutableList<Character> {

    private final String string;

    StringAsImmutableList(String string) {
      this.string = string;
    }

    @Override
    public int indexOf(@CheckForNull Object object) {