How to use the jupytext.cli.jupytext function in jupytext

def test_error_update_not_ipynb(tmp_py):
    with pytest.raises(ValueError, match='--update is only for ipynb files'):
        jupytext([tmp_py, '--to', 'py', '--update'])

def test_convert_and_update_preserves_notebook(nb_file, fmt, tmpdir):
    # cannot encode magic parameters in markdown yet
    if 'magic' in nb_file and fmt == 'md':
        return

    tmp_ipynb = str(tmpdir.join('notebook.ipynb'))
    copyfile(nb_file, tmp_ipynb)
    ext = long_form_one_format(fmt)['extension']
    tmp_text = str(tmpdir.join('notebook' + ext))

    jupytext(['--to', fmt, tmp_ipynb])
    jupytext(['--to', 'ipynb', '--update', tmp_text])

    nb_org = read(nb_file)
    nb_now = read(tmp_ipynb)
    compare(nb_now, nb_org)

def test_to_cpluplus(nb_file, tmpdir, capsys):
    nb_org = str(tmpdir.join(os.path.basename(nb_file)))
    copyfile(nb_file, nb_org)
    nb1 = read(nb_org)

    text_cpp = writes(nb1, 'cpp')
    jupytext([nb_org, '--to', 'c++', '--output', '-'])

    out, err = capsys.readouterr()
    assert err == ''
    compare(out, text_cpp)

def test_paired_paths(nb_file, tmpdir, capsys):
    tmp_ipynb = str(tmpdir.join('notebook.ipynb'))
    nb = read(nb_file)
    nb.metadata.setdefault('jupytext', {})['formats'] = 'ipynb,_light.py,_percent.py:percent'
    write(nb, tmp_ipynb)

    jupytext(['--paired-paths', tmp_ipynb])

    out, err = capsys.readouterr()
    assert not err

    formats = nb.metadata.get('jupytext', {}).get('formats')
    assert set(out.splitlines()).union([tmp_ipynb]) == set(
        [path for path, _ in paired_paths(tmp_ipynb, 'ipynb', formats)])

def test_cli_can_infer_jupytext_format(nb_file, ext, tmpdir):
    tmp_ipynb = str(tmpdir.join('notebook.ipynb'))
    tmp_text = str(tmpdir.join('notebook' + ext))
    nb = read(nb_file)

    # Light format to Jupyter notebook
    write(nb, tmp_text)
    jupytext(['--to', 'notebook', tmp_text])
    nb2 = read(tmp_ipynb)
    compare_notebooks(nb2, nb)

    # Percent format to Jupyter notebook
    write(nb, tmp_text, ext + ':percent')
    jupytext(['--to', 'notebook', tmp_text])
    nb2 = read(tmp_ipynb)
    compare_notebooks(nb2, nb)

def test_execute_readme_ok(tmpdir):
    tmp_md = str(tmpdir.join('notebook.md'))

    with open(tmp_md, 'w') as fp:
        fp.write("""
A readme with correct instructions

```python
1 + 2

""")

jupytext(args=[tmp_md, '--execute'])

def test_utf8_out_331(capsys):
    py = u"from IPython.core.display import HTML; HTML(u'\xd7')"

    with mock.patch('sys.stdin', StringIO(py)):
        jupytext(['--to', 'ipynb', '--execute', '-'])

    out, err = capsys.readouterr()
    assert err == ''
    nb = reads(out, 'ipynb')
    assert len(nb.cells) == 1
    print(nb.cells[0].outputs)
    assert nb.cells[0].outputs[0]['data']['text/html'] == u'\xd7'

def hook():
        with mock.patch('jupytext.cli.system', system_in_tmpdir):
            jupytext(['--to', 'py', '--pre-commit'])

def test_set_formats(py_file, tmpdir):
    tmp_py = str(tmpdir.join('notebook.py'))
    tmp_ipynb = str(tmpdir.join('notebook.ipynb'))

    copyfile(py_file, tmp_py)

    jupytext([tmp_py, '--set-formats', 'ipynb,py:light'])
    nb = read(tmp_ipynb)
    assert nb.metadata['jupytext']['formats'] == 'ipynb,py:light'

def test_apply_black_through_jupytext(tmpdir, nb_file):
    # Load real notebook metadata to get the 'auto' extension in --pipe-fmt to work
    metadata = read(nb_file).metadata

    nb_org = new_notebook(cells=[new_code_cell('1        +1')], metadata=metadata)
    nb_black = new_notebook(cells=[new_code_cell('1 + 1')], metadata=metadata)

    os.makedirs(str(tmpdir.join('notebook_folder')))
    os.makedirs(str(tmpdir.join('script_folder')))

    tmp_ipynb = str(tmpdir.join('notebook_folder').join('notebook.ipynb'))
    tmp_py = str(tmpdir.join('script_folder').join('notebook.py'))

    # Black in place
    write(nb_org, tmp_ipynb)
    jupytext([tmp_ipynb, '--pipe', 'black'])
    nb_now = read(tmp_ipynb)
    compare(nb_now, nb_black)

    # Write to another folder using dots
    script_fmt = os.path.join('..', 'script_folder//py:percent')
    write(nb_org, tmp_ipynb)
    jupytext([tmp_ipynb, '--to', script_fmt, '--pipe', 'black'])
    assert os.path.isfile(tmp_py)
    nb_now = read(tmp_py)
    nb_now.metadata = metadata
    compare(nb_now, nb_black)
    os.remove(tmp_py)

    # Map to another folder based on file name
    write(nb_org, tmp_ipynb)
    jupytext([tmp_ipynb, '--from', 'notebook_folder//ipynb', '--to', 'script_folder//py:percent',