docs: def build_augmented_stop_times(gtfsr_feeds, gtfs_feed, date):
      """
      Given a list of GTFSR feeds (FeedMessage instances), a GTFS feed
      (GTFSTK Feed instance), and a date (YYYYMMDD string), return
      a DataFrame of GTFS stop times for trips scheduled on the given date
      and containing two extra columns, ``'arrival_delay'`` and
      ``'departure_delay'``, which are delay values in seconds
      for that stop time according to the GTFSR feeds given.
  
      If no GTFSR feeds are given or if their dates don't alight with
      the given date, then the resulting delay fields will be all NaN.
      """
      # Get scheduled stop times for date
      st = gt.get_stop_times(gtfs_feed, date)
  
      # Get GTFSR timestamps pertinent to date.
      # Use datetime format YYYYMMDDHHMMSS to be compatible with GTFS dates
      datetime_format = '%Y%m%d%H%M%S'
      start_time = '000000'
      start_datetime = date + start_time
      # Plus 20 minutes fuzz:
      end_time = gt.timestr_to_seconds(st['departure_time'].max()) + 20*60
      if end_time >= 24*3600:
          end_date = str(int(date) + 1)
      else:
          end_date = date
      end_time = gt.timestr_to_seconds(end_time, inverse=True)
      end_time = gt.timestr_mod24(end_time)
      end_time = end_time.replace(':', '')
      end_datetime = end_date + end_time
  
      # Extract delays
      delays_frames = [extract_delays(f) for f in gtfsr_feeds
        if start_datetime <= get_timestamp_str(f, datetime_format)
        <= end_datetime]
  
      # Combine delays
      delays = combine_delays(delays_frames)
      if delays.empty:
          # Assign NaNs to delays
          ast = (
              st
              .assign(arrival_delay = np.nan)
              .assign(departure_delay = np.nan)
          )
      else:
          del delays['route_id']
  
          # Merge with stop times
          ast = st.merge(delays, how='left',
            on=['trip_id', 'stop_id', 'stop_sequence'])
  
      return ast.sort_values(['trip_id', 'stop_sequence'])