code: def short_form_one_format(jupytext_format):
      
      if not isinstance(jupytext_format, dict):
          return jupytext_format
      fmt = jupytext_format['extension']
      if 'suffix' in jupytext_format:
          fmt = jupytext_format['suffix'] + fmt
      elif fmt.startswith('.'):
          fmt = fmt[1:]
  
      if 'prefix' in jupytext_format:
          fmt = jupytext_format['prefix'] + '/' + fmt
  
      if jupytext_format.get('format_name'):
          if jupytext_format['extension'] not in ['.md', '.Rmd'] or jupytext_format['format_name'] == 'pandoc':
              fmt = fmt + ':' + jupytext_format['format_name']
  
      return fmt
docs: Represent one jupytext format as a string