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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 update(self, friendly_name=values.unset, sync_service_sid=values.unset):
 """ Update the DeploymentInstance :param unicode friendly_name: A human readable description for this Deployment. :param unicode sync_service_sid: The unique identifier of the Sync service instance. :returns: Updated DeploymentInstance :rtype: twilio.rest.preview.deployed_devices.fleet.deployment.DeploymentInstance """

        return self._proxy.update(friendly_name=friendly_name, sync_service_sid=sync_service_sid, )