Return a tuple that outputs a row of _FIELD_NAMES to be written to a
       SQLite database.

    Arguments:
        trip_id: The trip_id of the trip to which this StopTime corresponds.
                 It must be provided, as it is not stored in StopTime.

def GetSqlValuesTuple(self, trip_id):
    """Return a tuple that outputs a row of _FIELD_NAMES to be written to a
       SQLite database.

    Arguments:
        trip_id: The trip_id of the trip to which this StopTime corresponds.
                 It must be provided, as it is not stored in StopTime.
    """

    result = []
    for fn in self._SQL_FIELD_NAMES:
      if fn == 'trip_id':
        result.append(trip_id)
      else:
        # Since we'll be writting to SQLite, we want empty values to be
        # outputted as NULL string (contrary to what happens in
        # GetFieldValuesTuple)
        result.append(getattr(self, fn))
    return tuple(result)