@api.multi
    def button_confirm(self):
        """ Sobreescrita funcion para agregar nueva validacion de aprobacion
        de usuarios """
        for order in self:
            if order.state not in ['draft', 'sent']:
                continue
                order._add_supplier_to_product()
            # Deal with double validation process
            if order.company_id.po_double_validation == 'one_step'\
                    or (order.company_id.po_double_validation == 'two_step' and order.amount_total < self.env.user.company_id.currency_id.compute(order.company_id.po_double_validation_amount, order.currency_id)):
                order.button_approve()
            elif order.company_id.po_double_validation == 'user_approval' and self.amount_total > self.env.user.company_id.currency_id.compute(order.general_po_max, order.currency_id):
                # crea los usuarios que van a aprobar la orden de compra
                self.create_users_previous_approval_level()
                order.write({'state': 'to approve'})
                if self.check_user_one_approval():
                    order.button_approve()
                elif order.company_id.mail_purchase_approval_check:
                    self.get_url_purchase_order()
                    order.button_approve()
                    self.send_mail_to_user_approval()

            else:
                order.button_approve()
        return True