/** join two {@link Optional} with the same target */
public final <S1> Optional<Either<S, S1>, A> sum(final Optional<S1, A> other) {
return new Optional<>(pOptional.sum(other.pOptional));
}
/** join two {@link Optional} with the same target */
public final <S1> Optional<Either<S, S1>, A> sum(final Optional<S1, A> other) {
return new Optional<>(pOptional.sum(other.pOptional));
}