old_contents: # -*- coding: utf-8 -*-
  from openerp import api, fields, models
  
  class Stock(models.Model):
      _inherit = 'stock.picking'
  
      has_contract_hours = fields.Boolean(string="Has contract hours",
                                          compute="_compute_has_contract_hours")
new_contents: # -*- coding: utf-8 -*-
  from openerp import api, fields, models
  
  
  class Stock(models.Model):
      _inherit = 'stock.picking'
  
      provider_ref_id = fields.Char(string="Provider reference")
  
subject: Add provider_ref_id field