docs: def make_gtfs(source_path, target_path, buffer, ndigits):
      """
      Create a GTFS feed from the files in the directory SOURCE_PATH.
      See the project README for a description of the required source
      files.
      Save the feed to the file or directory TARGET_PATH.
      If the target path ends in '.zip', then write the feed as a zip
      archive.
      Otherwise assume the path is a directory, and write the feed as a
      collection of CSV files to that directory, creating the directory
      if it does not exist.
  
      If a stops file is present, then search within ``buffer`` meters
      on the traffic side of trip paths for stops.
      Round all decimals to ndigits decimal places.
      All distances in the resulting GTFS feed will be in kilometers.
      """
      pfeed = pf.read_protofeed(source_path)
      feed = m.build_feed(pfeed, buffer=buffer)
      gt.write_gtfs(feed, target_path, ndigits=ndigits)