How to get the correct vendor id at Checkout Page?

I success display chosen shipping method using the code below:

 $chosen_methods = WC()->session->chosen_shipping_methods;
 $chosen_shipping = $chosen_methods[5];
 echo '<pre>';
 echo print_r($chosen_methods);
 echo "<br><br>";
 echo print_r($chosen_shipping);
 echo '</pre>';

I will get the result show at below:

Array
(
    [18] => flat_rate:32
    [5] => local_pickup:30
    [19] => 
    [20] => free_shipping:22
)
1

local_pickup:301

Because the platform (WCFM) is multivendor, so inside array, it will display each vendor’s id: [18], [5], [19], [20] and their current chosen shipping method.

However, actually I only choose Vendor [5]’s product in cart page, so I expect to show the Shipping Method of Vendor [5] only.

May I ask: how to get the correct vendor id at Checkout Page?