I'm using woocommerce and dokan plugin in wordpress.
After I try to order product in multi vendor, I get the sub order number in thank you page.
I try to get sub order number by running this code below but not work.

```
//example order id
$order = wc_get_order(1234);

$order_id = $order->get_id();

$sub_orders = get_children( 
   array(    
     'post_parent' => $order_id,    
     'post_type'   => 'shop_order',    
     'post_status' => array( 
        'wc-pending', 
        'wc-completed', 
        'wc-processing', 
        'wc-on-hold' 
       )
   ) 
);

```

when i try `var_dump($sub_order)` i got 0 array result.
is any way to get sub order?