old_contents: """Read and write Jupyter notebooks as text files"""
  
  from .jupytext import readf, writef, writes, reads
  from .formats import NOTEBOOK_EXTENSIONS, guess_format, get_format_implementation
  from .version import __version__
  
  try:
      from .contentsmanager import TextFileContentsManager
  except ImportError as err:
      class TextFileContentsManager:
          """A class that raises the previous ImportError"""
          err = err
  
          def __init__(self):
              raise self.err
  
  __all__ = ['readf', 'writef', 'writes', 'reads',
             'NOTEBOOK_EXTENSIONS', 'guess_format', 'get_format_implementation',
             'TextFileContentsManager', '__version__']
  
new_contents: """Read and write Jupyter notebooks as text files"""
  
  from .jupytext import readf, writef, writes, reads
  from .formats import NOTEBOOK_EXTENSIONS, guess_format, get_format_implementation
  from .version import __version__
  
  try:
      from .contentsmanager import TextFileContentsManager
  except ImportError as err:
      class TextFileContentsManager:
          """A class that raises the previous ImportError"""
          err = err
  
          def __init__(self):
              raise self.err
  
  def _jupyter_nbextension_paths():
      """Allows commands like
       jupyter nbextension install --py jupytext
       jupyter nbextension enable --py jupytext
       jupyter labextension install jupyterlab-jupytext"""
      return [dict(
          section="notebook",
          # the path is relative to the `jupytext` directory
          src="nbextension",
          # directory in the `nbextension/` namespace
          dest="jupytext",
          # _also_ in the `nbextension/` namespace
          require="jupytext/index")]
  
  
  __all__ = ['readf', 'writef', 'writes', 'reads',
             'NOTEBOOK_EXTENSIONS', 'guess_format', 'get_format_implementation',
             'TextFileContentsManager', '__version__']
  
subject: Allow "jupyter nbextension install/enable --py jupytext"