Attach core filters to filterset

def attach_core_filters(cls):
        """
        Attach core filters to filterset
        """
        opts = cls._meta
        base_filters = cls.base_filters.copy()
        cls.base_filters.clear()
        for name, filter_ in six.iteritems(base_filters):
            if isinstance(filter_, AutoFilters):
                field = filterset.get_model_field(opts.model, filter_.name)
                filter_exclusion = filter_.extra.pop('drop', [])
                for lookup_expr in utils.lookups_for_field(field):
                    if lookup_expr not in filter_exclusion:
                        new_filter = cls.filter_for_field(field, filter_.name, lookup_expr)
                        # by convention use field name for filters with exact lookup_expr
                        if lookup_expr != 'exact':
                            filter_name = LOOKUP_SEP.join([name, lookup_expr])
                        else:
                            filter_name = name
                        cls.base_filters[filter_name] = new_filter