code: def route_frequencies(gtfs, results_by_mode=False):
      
      day = gtfs.get_suitable_date_for_daily_extract()
      query = (
          " SELECT f.route_I, type, frequency FROM routes as r"
          " JOIN"
          " (SELECT route_I, COUNT(route_I) as frequency"
          " FROM"
          " (SELECT date, route_I, trip_I"
          " FROM day_stop_times"
          " WHERE date = '{day}'"
          " GROUP by route_I, trip_I)"
          " GROUP BY route_I) as f"
          " ON f.route_I = r.route_I"
          " ORDER BY frequency DESC".format(day=day))
      
      return pd.DataFrame(gtfs.execute_custom_query_pandas(query))
docs: Return the frequency of all types of routes per day.
  
      Parameters
      -----------
      gtfs: GTFS
  
      Returns
      -------
      pandas.DataFrame with columns
          route_I, type, frequency