code: def tripI_takes_place_on_dsut(self, trip_I, day_start_ut):
          
          query = "SELECT * FROM days WHERE trip_I=? AND day_start_ut=?"
          params = (trip_I, day_start_ut)
          cur = self.conn.cursor()
          rows = list(cur.execute(query, params))
          if len(rows) == 0:
              return False
          else:
              assert len(rows) == 1, 'On a day, a trip_I should be present at most once'
              return True
docs: Check that a trip takes place during a day
  
          Parameters
          ----------
          trip_I : int
              index of the trip in the gtfs data base
          day_start_ut : int
              the starting time of the day in unix time (seconds)
  
          Returns
          -------
          takes_place: bool
              boolean value describing whether the trip takes place during
              the given day or not