Fortnox - Only Bookeep orders that has Swish as Payment Method

functions.php

<?php
/**
* @snippet WooCommerce - Fortnox plugin by Redlight Media - Bookeep only Swish Orders
* @author Redlight Media AB / Christopher Hedqvist
* @compatible WooCommerce 4.2.0
*/
function redlight_fortnox_bookeep_swish($should_bookeep,$order_id, $updated_order) {
    $order = wc_get_order($order_id);
    $order_payment_method = $order->get_payment_method();
    switch( $order_payment_method ) {
        case 'redlight_swish':
        case 'redlight_swish-ecommerce':
            $should_bookeep = true;
            break;
        default:
            $should_bookeep = false;
    }
    
    return $should_bookeep;
}
add_filter('obj_fortnox_create_order_bookeep_invoice', 'redlight_fortnox_bookeep_swish', 10, 3 );