I'm trying to add a custom field('destination') into orderline tree but it doesn't function (error: Invalid XML for View Architecture) This is my script

<record model="ir.ui.view" id="edit_order_line_tree">
        <field name="name">purchase.order.tree.inherit</field>
        <field name="model">purchase.order</field>
     <field name="type">tree</field>
        <field name="inherit_orderid" ref="purchase.purchase_order_tree"/>
        <field name="arch" type="xml">
         <xpath expr="/form/sheet/tree/field[@name='price_subtotal']" position="before">
                <field name="destination" />
         </xpath>
        </field>
   </record>