@fields.depends('reservation','tickets')
    def on_change_reservation(self):
        pool = Pool()
        Ticket = pool.get('ticket.ticket')
        if self.reservation:
            tkts = list(self.tickets)
            for t in self.reservation.tickets:
                nt = Ticket()
                # Copy all the fields value from t to nt
                tkts.append(nt)
            self.tickets = tuple(tkts)