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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 fetch_points_of_sales(self, ticket=None):
 """ Fetch all point of sales objects. Fetch all point of sales from the WS and store (or update) them locally. Returns a list of tuples with the format (pos, created,). """

        ticket = ticket or self.get_or_create_ticket('wsfe')

        client = clients.get_client('wsfe', self.is_sandboxed)
        response = client.service.FEParamGetPtosVenta(
            serializers.serialize_ticket(ticket),
        )
        check_response(response)

        results = []
        for pos_data in response.ResultGet.PtoVenta:
            results.append(PointOfSales.objects.update_or_create(
                number=pos_data.Nro,
                issuance_type=pos_data.EmisionTipo,
                owner=self,
                defaults={
                    'blocked': pos_data.Bloqueado == 'N',
                    'drop_date': parsers.parse_date(pos_data.FchBaja),
                }
            ))

        return results