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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 archive(cwd, output, rev='tip', fmt=None, prefix=None, user=None):
    '''
    Export a tarball from the repository

    cwd
        The path to the Mercurial repository

    output
        The path to the archive tarball

    rev: tip
        The revision to create an archive from

    fmt: None
        Format of the resulting archive. Mercurial supports: tar,
        tbz2, tgz, zip, uzip, and files formats.

    prefix : None
        Prepend <prefix>/ to every filename in the archive

    user : None
        Run hg as a user other than what the minion runs as

    If ``prefix`` is not specified it defaults to the basename of the repo
    directory.

    CLI Example:

    .. code-block:: bash

        salt '*' hg.archive /path/to/repo output=/tmp/archive.tgz fmt=tgz
    '''
    cmd = [
            'hg',
            'archive',
            '{0}'.format(output),
            '--rev',
            '{0}'.format(rev),
            ]
    if fmt:
        cmd.append('--type')
        cmd.append('{0}'.format(fmt))
    if prefix:
        cmd.append('--prefix')
        cmd.append('"{0}"'.format(prefix))
    return __salt__['cmd.run'](cmd, cwd=cwd, runas=user, python_shell=False)