Download `url` to `fname` if `dest` doesn't exist, and un-tgz to folder `dest`.

def untar_data(url:str, fname:PathOrStr=None, dest:PathOrStr=None, data=True, force_download=False) -> Path:
    "Download `url` to `fname` if `dest` doesn't exist, and un-tgz to folder `dest`."
    dest = url2path(url, data) if dest is None else Path(dest)/url2name(url)
    fname = Path(ifnone(fname, _url2tgz(url, data)))
    if force_download or (fname.exists() and url in _checks and _check_file(fname) != _checks[url]):
        print(f"A new version of the {'dataset' if data else 'model'} is available.")
        if fname.exists(): os.remove(fname)
        if dest.exists(): shutil.rmtree(dest)
    if not dest.exists():
        fname = download_data(url, fname=fname, data=data)
        if url in _checks:
            assert _check_file(fname) == _checks[url], f"Downloaded file {fname} does not match checksum expected! Remove that file from {Config().data_archive_path()} and try your code again."
        tarfile.open(fname, 'r:gz').extractall(dest.parent)
    return dest