Do not sync retailer product (where SKU ends in _1)

functions.php

<?
function check_sync_woocommerce_product($check, $product_id){
  
    $wc_product = wc_get_product($product_id);

    $sku  = $wc_product->get_sku();
    $sku_chnk = explode('_', $sku);
    $to_sync  = (int) end($sku_chnk) == 1 ? false : true;
    if($to_sync){
        return $check;
    } else {
        add_filter( 'obj_fortnox_sync_product_data_error', function($message, $product_id, $wc_product){
          $message['message'] = __('This product is for retailers sales and can not be syncronized.', 'fortnox');
          return $message;
        }, 20, 3 );
        return false;
    }
  
}
add_filter('obj_fortnox_sync_product_data', 'check_sync_woocommerce_product', 10,2);