gn = (fn) => {
                const obj = {};
                for (const [name, x] of col_iter()) {
                    obj[colname(name, x)] = fn(name, x);
                }
                return obj;
            };

            const new_schema = () => assign((x) => x);

            let string_cache;
            function reset_strings_cache() {
                string_cache = {};
            }

            reset_strings_cache();

            const get_dict = (xs) => {
                string_cache[xs] = s