How to use the @lumino/algorithm.StringExt.highlight function in @lumino/algorithm

formatHeader(data: IHeaderRenderData): h.Child {
      if (!data.indices || data.indices.length === 0) {
        return data.category;
      }
      return StringExt.highlight(data.category, data.indices, h.mark);
    }

private _filter(): IIterator {
    let options = this._options || [];
    let query = this._query;
    if (!query) {
      return map(options, option => ({ raw: option, text: option }));
    }
    let results: Private.IMatch[] = [];
    for (let option of options) {
      let match = StringExt.matchSumOfSquares(option, query);
      if (match) {
        let marked = StringExt.highlight(option, match.indices, Private.mark);
        results.push({
          raw: option,
          score: match.score,
          text: marked.join('')
        });
      }
    }
    return map(results.sort(Private.scoreCmp), result => ({
      text: result.text,
      raw: result.raw
    }));
  }

formatItemLabel(data: IItemRenderData): h.Child {
      if (!data.indices || data.indices.length === 0) {
        return data.item.label;
      }
      return StringExt.highlight(data.item.label, data.indices, h.mark);
    }