code: def print_languages(ctx, param, value):
      
      if not value or ctx.resilient_parsing:
          return
      try:
          langs = tts_langs()
          langs_str_list = sorted("{}: {}".format(k, langs[k]) for k in langs)
          click.echo('  ' + '\n  '.join(langs_str_list))
      except RuntimeError as e:  # pragma: no cover
          log.debug(str(e), exc_info=True)
          raise click.ClickException("Couldn't fetch language list.")
      ctx.exit()
docs: Callback for <all> flag.
      Prints formatted sorted list of supported languages and exits