Following is my code and the changes are not reflecting in Sale->Order (Tree view on that page)

<record id = "sale_order_view_inherit" model = "ir.ui.view" > 
<field name = "name" > sale.order.view.inherit1 </ field > 
<field name = "model" > sale.order.line < / field > 
<field name = "inherit_id" ref = "sale_stock.view_order_line_tree_inherit_sale_stock" /> 
<field name = "arch" type = "xml" > 
  <field name = "price_unit" position= "after" > 
      < field name = "trade_offer" /> 
  </field > 
    </field >
</record>

I want to add a field after price_unit field in the tree view of Sale->order tree view