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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 add_service_port(service, port):
    '''
    Add a new port to the specified service.

    .. versionadded:: 2016.11.0

    CLI Example:

    .. code-block:: bash

        salt '*' firewalld.add_service_port zone 80
    '''
    if service not in get_services(permanent=True):
        raise CommandExecutionError('The service does not exist.')

    cmd = '--permanent --service={0} --add-port={1}'.format(service, port)
    return __firewall_cmd(cmd)