i added the serial_no field stock.moves

model

class StockMove(models.Model):

    _inherit = "stock.move" 

   serial_no = fields.Char(string="Serial#", readonly=True)

I use onchange function to pass values from product to movelines

onchange

@api.onchange('product_id')

    def on_change_product(self):

           self.serial_no = self.product_id.serial_no

Then i used the create method to save these values
create 

@api.model

    def create(self, vals):

        product_obj = self.env['product.product']

        product_records = product_obj.search([])

        for record in product_records:

            vals['serial_no'] = record.serial_no

        res = super(StockMove, self).create(vals)

        return res

notes

the serial no field is not saved.How to save the field?
please help to find what is wrong in my code?