如何使用odoo 8.0中的上下文默认显示销售订单行中的销售订单字段？

I have a field named sales_ship under sale.order model and another field named ship_sale in the sale.order.line. Now what I want is to have the selected sales_ship in the sales.order to come by default in the ship_sale in the sale.order.line by default. How to do it by using context? Here is my full code.I have a field named sales_ship under sale.orde