docs: def write_gtfsr(feed, path, *, to_json=False):
      """
      Given a GTFSR feed (FeedMessage instance), write it to the given
      file path (string or Path object).
      If ``to_json``, then save the file as JSON;
      otherwise save it as Protocol Buffer.
      """
      path = Path(path)
  
      if to_json:
          with path.open('w') as tgt:
              tgt.write(json_format.MessageToJson(feed))
      else:
          with path.open('wb') as tgt:
              tgt.write(feed.SerializeToString())