private function getArgsForAttempt($attempt)
    {
        $args = $this->args;

        // Determine the delay.
        $delay = ($attempt === 1)
            ? $this->config['initDelay']
            : $this->config['delay'];
        if (is_callable($delay)) {
            $delay = $delay($attempt);
        }

        // Set the delay. (Note: handlers except delay in milliseconds.)
        if (!isset($args['@http'])) {
            $args['@http'] = [];
        }
        $args['@http']['delay'] = $delay * 1000;

        return $args;
    }