code: def get_lookup(self, main_field, for_remote, alias):
          
          lookup_class = for_remote.get_lookup("exact")
          return lookup_class(for_remote.get_col(alias), self.value)
docs: create a fake field for the lookup capability
          :param CompositeForeignKey main_field: the local fk
          :param Field for_remote: the remote field to match
          :return: