otherwise example

    public function then(
        callable $onFulfilled = null,
        callable $onRejected = null
    ): PromiseInterface {
        return $this->result->then($onFulfilled, $onRejected);
    }

    public function otherwise(callable $onRejected): PromiseInterface
    {
        return $this->result->otherwise($onRejected);
    }

    public function wait(bool $unwrap = true)
    {
        return $this->result->wait($unwrap);
    }

    public function getState(): string
    {
        return $this->result->getState();
    }