code: def transitions(self, year):
          
  
          if not self.hasdst:
              return None
  
          dston = picknthweekday(year, self._dstmonth, self._dstdayofweek,
                                 self._dsthour, self._dstminute,
                                 self._dstweeknumber)
  
          dstoff = picknthweekday(year, self._stdmonth, self._stddayofweek,
                                  self._stdhour, self._stdminute,
                                  self._stdweeknumber)
  
          # Ambiguous dates default to the STD side
          dstoff -= self._dst_base_offset
  
          return dston, dstoff
docs: For a given year, get the DST on and off transition times, expressed
          always on the standard time side. For zones with no transitions, this
          function returns ``None``.
  
          :param year:
              The year whose transitions you would like to query.
  
          :return:
              Returns a :class:`tuple` of :class:`datetime.datetime` objects,
              ``(dston, dstoff)`` for zones with an annual DST transition, or
              ``None`` for fixed offset zones.