Items in purchase order based on Default Supplier

I want to setup the purchase order to fetch items based on the supplier name. The following post is shared but when i put all the coding in the backend the purchase order is shown empty. Can someone help me regarding this.

P.s. https://erpnext.org/docs/user/manual/en/buying/articles/pull-items-in-purchase-order-based-on-supplier
This option is not visible on version 10. Please help

Anyone please ?

The functionality that the button For Supplier used to do is the same as what Get Items from Open Material Requests does. Goto Purchase Order and select the Supplier - A button will become visible that will fetch data for that Supplier.

Thank you for your kind reply Zlash, my query is that I want to show only the item releated to the supplier in the purchase order without making the material request or something. Just choose the supplier in PO and the items visible in the child table of items must only be for that supplier

Anyone ? please help