public function getGuestCheckoutSessionRequest($checkout_session_id, $x_ebay_c_marketplace_id)
    {
        // Verify the required parameter 'checkout_session_id' is set.
        if ($checkout_session_id === null || (\is_array($checkout_session_id) && count($checkout_session_id) === 0)) {
            throw new \InvalidArgumentException('Missing the required parameter $checkout_session_id when calling getGuestCheckoutSession');