selectorForAnnotation = ( cell, annotation) => {
          let cellAttr = 'data-code-cell="' + cell + '"';
          let lineAttr = 'data-code-annotation="' +  annotation + '"';
          const selector = 'span[' + cellAttr + '][' + lineAttr + ']';
          return selector;
        }
        const selectCodeLines = (annoteEl) => {
          const doc = window.document;
          const targetCell = annoteEl.getAttribute("data-target-cell");
          const targetAnnotation = annoteEl.getAttribute("data-targ