I am using odoo community version 12

I tried creating two different Id's using two different create functions in a single model. But, it generates only one of them at a time.

bill_num=fields.Char(string='Bill Id',Translate=True, readonly=True)
   

class orders(models.Model):

    @api.model
    def create(self, vals):
        x = self.env['ir.sequence'].next_by_code('pickabite.orders') or '/'
        vals['bill_num'] = x
        return super(orders,self).create(vals)
   
   
    #order id generation
    order_id = fields.Char(string='Order Id', Translate= True ,
            readonly = True)
           
    @api.model
    def create(self, vals):
        x = self.env['ir.sequence'].next_by_code('pickabite.orders') or '/'
        vals['order_id'] = x
        return super(orders,self).create(vals)