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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 update_jail(name):
    '''
    Run freebsd-update on `name` poudriere jail

    CLI Example:

    .. code-block:: bash

        salt '*' poudriere.update_jail freebsd:10:x86:64
    '''
    if is_jail(name):
        cmd = 'poudriere jail -u -j {0}'.format(name)
        ret = __salt__['cmd.run'](cmd)
        return ret
    else:
        return 'Could not find jail {0}'.format(name)