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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 build_services(did, service_descriptors):
 """ Build a list of services. :param did: DID, str :param service_descriptors: List of tuples of length 2. The first item must be one of ServiceTypes and the second item is a dict of parameters and values required by the service :return: List of Services """

        services = []
        sa_def_key = ServiceAgreement.SERVICE_DEFINITION_ID
        for i, service_desc in enumerate(service_descriptors):
            service = ServiceFactory.build_service(service_desc, did)
            # set serviceDefinitionId for each service
            service.update_value(sa_def_key, str(i))
            services.append(service)

        return services