{"ast_node_type":"variable","tokens":[{"end":74,"kind":"keyword","start":0,"text":"let"}]}
    let input_ts = parse_string(call_site, input).into_subtree(call_site);
    let mixed_site = TokenId(2);
    let attr_ts = attr.map(|attr| parse_string(call_site, attr).into_subtree(call_site));