code: def hourly_frequencies(gtfs, st, et, route_type):
       
      timeframe = et-st
      hours = timeframe/ 3600
      day = gtfs.get_suitable_date_for_daily_extract()
      stops = gtfs.get_stops_for_route_type(route_type).T.drop_duplicates().T
      query = ("SELECT * FROM stops as x"
               " JOIN"
               " (SELECT * , COUNT(*)/{h} as frequency"
               " FROM stop_times, days"
               " WHERE stop_times.trip_I = days.trip_I"
               " AND dep_time_ds > {st}"
               " AND dep_time_ds < {et}"
               " AND date = '{day}'"
               " GROUP BY stop_I) as y"
               " ON y.stop_I = x.stop_I".format(h=hours, st=st, et=et, day=day))
      try:
          trips_frequency = gtfs.execute_custom_query_pandas(query).T.drop_duplicates().T
          df = pd.merge(stops[['stop_I', 'lat', 'lon']], trips_frequency[['stop_I', 'frequency']],
                        on='stop_I', how='inner')
          return df.apply(pd.to_numeric)
      except:
          raise ValueError("Maybe too short time frame!")
docs: Return all the number of vehicles (i.e. busses,trams,etc) that pass hourly through a stop in a time frame.
  
      Parameters
      ----------
      gtfs: GTFS
      st : int
          start time of the time framein unix time
      et : int
          end time of the time frame in unix time
      route_type: int
  
      Returns
      -------
      numeric pandas.DataFrame with columns
          stop_I, lat, lon, frequency