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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def process_ticket(self):
 """ fetch the ticket against the database and check its validity :raises ValidateError: if the ticket is not found or not valid, potentially for that service :returns: A couple (ticket, proxies list) :rtype: :obj:`tuple` """

        try:
            proxies = []
            if self.allow_proxy_ticket:
                ticket = models.Ticket.get(self.ticket, self.renew)
            else:
                ticket = models.ServiceTicket.get(self.ticket, self.renew)
            try:
                for prox in ticket.proxies.all():
                    proxies.append(prox.url)
            except AttributeError:
                pass
            if ticket.service != self.service:
                raise ValidateError(u'INVALID_SERVICE', self.service)
            return ticket, proxies
        except Ticket.DoesNotExist:
            raise ValidateError(u'INVALID_TICKET', self.ticket)
        except (ServiceTicket.DoesNotExist, ProxyTicket.DoesNotExist):
            raise ValidateError(u'INVALID_TICKET', 'ticket not found')