 - 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.createElement("div");
              div.setAttribute("id", "code-annotation-line-highlight");
           