code: def unlocalized_datetime_to_ut_seconds(self, unlocalized_datetime):
          
          loc_dt = self._timezone.localize(unlocalized_datetime)
          unixtime_seconds = calendar.timegm(loc_dt.utctimetuple())
          return unixtime_seconds
docs: Convert datetime (in GTFS timezone) to unixtime
  
          Parameters
          ----------
          unlocalized_datetime : datetime.datetime
              (tz coerced to GTFS timezone, should NOT be UTC.)
  
          Returns
          -------
          output : int (unixtime)