public function toValueHolder(array $metadata = []): SplitTokenValueHolder
    {
        if (null === $this->verifierHash) {
            throw new \RuntimeException('toValueHolder() does not work SplitToken object created with fromString().');
        }

        return new SplitTokenValueHolder($this->selector, $this->verifierHash, $this->expiresAt, $metadata, $this);
    }