{"ast_node_type":"variable","tokens":[{"end":90,"kind":"keyword","start":0,"text":"let"}]}
            let close_brace_span = sm.span_look_ahead(followed_brace_span, "}", Some(50));
            // by parentheses, find the appropriate span.
            let closing_brace = close_brace_span.map(|sp| span.to(sp));