@Nonnull
    public Optional<T> asOptional() {
        return isPresent() ? Optional.ofNullable(this.value) : Optional.empty();
    }
If a value is present in this {@link NullableOptional}, returns the result
of passing the value to {@link Optional#ofNullable(Object)}. Otherwise returns
an empty optional.

@return an {@link Optional} representing the value held by this {@link NullableOptional}

@see Optional#ofNullable(Object)
helper/src/main/java/me/lucko/helper/utils/NullableOptional.java