{"ast_node_type":"function","tokens":[{"end":41,"kind":"keyword","start":0,"text":"fn"}]}
        fn list(ns: &[usize]) -> String {
        // E.g. `[4, 4, 4, 3, 2, 1, 1, 1, 1, 1]` -> "[4 (x3), 3, 2, 1 (x5)]".
            let mut v = Vec::new();