def get_choices_add(self, qs):
        count_dict = self.get_values_counts(qs)
        return [FilterChoice(self.render_choice_object(val),
                             count,
                             self.build_params(add=val),
                             FILTER_ADD)
                for val, count in count_dict.items()
                for val in (NullChoice if val is None else val,)]
Called by 'get_choices', this is usually the one to override.
dataset/ETHPy150Open ionelmc/django-easyfilters/src/django_easyfilters/filters.py/ValuesFilter.get_choices_add