{
              const lastEl = window.document.getElementById(lineIds[lineIds.length - 1]);
              const bottom = lastEl.offsetTop + lastEl.offsetHeight;
              height = bottom - top;
            }
            if (top !== null && height !== null && parent !== null) {
              // cook up a div (if necessary) and position it 
              let div = window.document.getElementById("code-annotation-line-highlight");
              if (div === null) {
                div = window.document.creat