docs: def save(self, model, path=''):
          """Save the file model and return the model with no content."""
          if model['type'] != 'notebook':
              return super(TextFileContentsManager, self).save(model, path)
  
          nbk = model['content']
          try:
              metadata = nbk.get('metadata')
              rearrange_jupytext_metadata(metadata)
              jupytext_metadata = metadata.setdefault('jupytext', {})
              jupytext_formats = jupytext_metadata.get('formats') or self.default_formats(path)
  
              if not jupytext_formats:
                  text_representation = jupytext_metadata.get('text_representation', {})
                  ext = os.path.splitext(path)[1]
                  fmt = {'extension': ext}
  
                  if ext == text_representation.get('extension') and text_representation.get('format_name'):
                      fmt['format_name'] = text_representation.get('format_name')
  
                  jupytext_formats = [fmt]
  
              jupytext_formats = long_form_multiple_formats(jupytext_formats, metadata)
  
              # Set preferred formats if not format name is given yet
              jupytext_formats = [preferred_format(fmt, self.preferred_jupytext_formats_save) for fmt in jupytext_formats]
  
              base, fmt = find_base_path_and_format(path, jupytext_formats)
              self.update_paired_notebooks(path, fmt, jupytext_formats)
              self.set_default_format_options(jupytext_metadata)
  
              if not jupytext_metadata:
                  metadata.pop('jupytext')
  
              # Save as ipynb first
              return_value = None
              value = None
              for fmt in jupytext_formats[::-1]:
                  if fmt['extension'] != '.ipynb':
                      continue
  
                  alt_path = full_path(base, fmt)
                  self.create_prefix_dir(alt_path, fmt)
                  self.log.info("Saving %s", os.path.basename(alt_path))
                  value = super(TextFileContentsManager, self).save(model, alt_path)
                  if alt_path == path:
                      return_value = value
  
              # And then to the other formats, in reverse order so that
              # the first format is the most recent
              for fmt in jupytext_formats[::-1]:
                  if fmt['extension'] == '.ipynb':
                      continue
  
                  alt_path = full_path(base, fmt)
                  self.create_prefix_dir(alt_path, fmt)
                  if 'format_name' in fmt and fmt['extension'] not in ['.Rmd', '.md']:
                      self.log.info("Saving %s in format %s:%s",
                                    os.path.basename(alt_path), fmt['extension'][1:], fmt['format_name'])
                  else:
                      self.log.info("Saving %s", os.path.basename(alt_path))
                  with mock.patch('nbformat.writes', _jupytext_writes(fmt)):
                      value = super(TextFileContentsManager, self).save(model, alt_path)
                      if alt_path == path:
                          return_value = value
  
              # Update modified timestamp to match that of the pair #207
              return_value['last_modified'] = value['last_modified']
              return return_value
  
          except Exception as err:
              raise HTTPError(400, str(err))