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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 _get_migrate_command():
    '''
    Returns the command shared by the different migration types
    '''
    tunnel = __salt__['config.option']('virt.tunnel')
    if tunnel:
        salt.utils.versions.warn_until(
            'Sodium',
            '\'virt.tunnel\' has been deprecated in favor of '
            '\'virt:tunnel\'. \'virt.tunnel\' will stop '
            'being used in {version}.')
    else:
        tunnel = __salt__['config.get']('virt:tunnel')
    if tunnel:
        return ('virsh migrate --p2p --tunnelled --live --persistent '
                '--undefinesource ')
    return 'virsh migrate --live --persistent --undefinesource '