949         if constant.type in ('Date', 'Datetime'):

   949         if constant.type in ('Date', 'Datetime'):

   950             rel = constant.relation()

   950             rel = constant.relation()

   951             if rel is not None:

   951             if rel is not None:

   952                 rel._q_needcast = value

   952                 rel._q_needcast = value

   953             return self.keyword_map[value]()

   953             return self.keyword_map[value]()

   954         if constant.type == 'Substitute':

   956         if constant.type == 'Substitute':

   955             _id = constant.value

   957             _id = constant.value

   956             if isinstance(_id, unicode):

   958             if isinstance(_id, unicode):

   957                 _id = _id.encode()

   959                 _id = _id.encode()

   958         else:

   960         else: