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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 deactivate_license(key_name=None):
    '''
    Deactivates an installed license.
    Required version 7.0.0 or greater.

    key_name(str): The file name of the license key installed.

    CLI Example:

    .. code-block:: bash

        salt '*' panos.deactivate_license key_name=License_File_Name.key

    '''

    _required_version = '7.0.0'
    if not __proxy__['panos.is_required_version'](_required_version):
        return False, 'The panos device requires version {0} or greater for this command.'.format(_required_version)

    if not key_name:
        return False, 'You must specify a key_name.'
    else:
        query = {'type': 'op', 'cmd': '<request><license><deactivate><key><features><member>{0}</member></features>'
                                      '</key></deactivate></license></request>'.format(key_name)}

    return __proxy__['panos.call'](query)