def prepare_sorting_fields(self):
        if self.sorting_parameter_name in self.request.query_params:
            self._sorting_fields = [
                _.strip() for _ in self.request.query_params.get(self.sorting_parameter_name).split(',')
            ]
        if self._sorting_fields:
            self._sorting_fields = [
                (self.sorting_fields_map.get(field.lstrip('-'), field.lstrip('-')), field[0] == '-')
                for field in self._sorting_fields
            ]