public function getUnsigned()
    {
        $payload = [];

        foreach ($this->data as $key => $value) {
            if (in_array($key, $this->accessors)) {
                $payload[$key] = $value;
            } elseif (in_array($key, $this->customFields)) {
                $payload['custom.'.$key] = $value;
            }
        }

        return QueryString::normalize($payload);
    }