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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_timezone(tz=None, deploy=False):
    '''
    Set the timezone of the Palo Alto proxy minion. A commit will be required before this is processed.

    CLI Example:

    Args:
        tz (str): The name of the timezone to set.

        deploy (bool): If true then commit the full candidate configuration, if false only set pending change.

    .. code-block:: bash

        salt '*' panos.set_timezone UTC
        salt '*' panos.set_timezone UTC deploy=True

    '''

    if not tz:
        raise CommandExecutionError("Timezone name option must not be none.")

    ret = {}

    query = {'type': 'config',
             'action': 'set',
             'xpath': '/config/devices/entry[@name=\'localhost.localdomain\']/deviceconfig/system/timezone',
             'element': '<timezone>{0}</timezone>'.format(tz)}

    ret.update(__proxy__['panos.call'](query))

    if deploy is True:
        ret.update(commit())

    return ret