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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 set_power_save(self, power_saving, wait_for_completion=True, operation_timeout=None):
 """ Set the power save setting of this CPC. The current power save setting in effect for a CPC is described in the "cpc-power-saving" property of the CPC. This method performs the HMC operation "Set CPC Power Save". It requires that the feature "Automate/advanced management suite" (FC 0020) is installed and enabled, and fails otherwise. This method will also fail if the CPC is under group control. Whether a CPC currently allows this method is described in the "cpc-power-save-allowed" property of the CPC. Authorization requirements: * Object-access permission to this CPC. * Task permission for the "Power Save" task. Parameters: power_saving (:term:`string`):
 The new power save setting, with the possible values: * "high-performance" - The power consumption and performance of the CPC are not reduced. This is the default setting. * "low-power" - Low power consumption for all components of the CPC enabled for power saving. * "custom" - Components may have their own settings changed individually. No component settings are actually changed when this mode is entered. wait_for_completion (bool):
 Boolean controlling whether this method should wait for completion of the requested asynchronous HMC operation, as follows: * If `True`, this method will wait for completion of the asynchronous job performing the operation. * If `False`, this method will return immediately once the HMC has accepted the request to perform the operation. operation_timeout (:term:`number`):
 Timeout in seconds, for waiting for completion of the asynchronous job performing the operation. The special value 0 means that no timeout is set. `None` means that the default async operation timeout of the session is used. If the timeout expires when `wait_for_completion=True`, a :exc:`~zhmcclient.OperationTimeout` is raised. Returns: `None` or :class:`~zhmcclient.Job`: If `wait_for_completion` is `True`, returns `None`. If `wait_for_completion` is `False`, returns a :class:`~zhmcclient.Job` object representing the asynchronously executing job on the HMC. Raises: :exc:`~zhmcclient.HTTPError`: See the HTTP status and reason codes of operation "Set CPC Power Save" in the :term:`HMC API` book. :exc:`~zhmcclient.ParseError` :exc:`~zhmcclient.AuthError` :exc:`~zhmcclient.ConnectionError` :exc:`~zhmcclient.OperationTimeout`: The timeout expired while waiting for completion of the operation. """

        body = {'power-saving': power_saving}
        result = self.manager.session.post(
            self.uri + '/operations/set-cpc-power-save',
            body,
            wait_for_completion=wait_for_completion,
            operation_timeout=operation_timeout)
        if wait_for_completion:
            # The HMC API book does not document what the result data of the
            # completed job is. It turns out that the completed job has this
            # dictionary as its result data:
            #    {'message': 'Operation executed successfully'}
            # We transform that to None.
            return None
        return result