docs: private ImmutableMap<Integer, Integer> lightEREOffsetToEDTOffset(String document) {
      final ImmutableMap.Builder<Integer, Integer> offsetMap = ImmutableMap.builder();
      int EDT = 0;
      // lightERE treats these as one, not two (as an XML parser would)
      document = document.replaceAll("\\r\\n", "\n");
      for (int i = 0; i < document.length(); i++) {
        final String c = document.substring(i, i + 1);
        // skip <tags>
        if (c.equals("<")) {
          i = document.indexOf('>', i);
          continue;
        }
        offsetMap.put(i, EDT);
        EDT++;
      }
      return offsetMap.build();
    }