How to use the subtitle/lib/stringify function in subtitle

function* subtitlesReloadSaga (_action) {
  const scope = yield select(state => state.get('scope'));
  const {selectedKey: key, availableOptions} = yield select(state => state.get('subtitles'));
  if (key) {
    /* Generate an initial item covering the entire recording (needed because
       the editor works by splitting existing items at a specific position). */
    let text = (availableOptions[key].text || '').trim();
    if (!text) {
      const data = yield select(state => state.getIn(['player', 'data']));
      text = srtStringify([{start: 0, end: data.events[data.events.length - 1][0], text: ''}]);
    }
    yield put({type: scope.subtitlesLoadFromText, payload: {key, text}});
  }
}

return state.update('subtitles', function (subtitles) {
    const {selectedKey: key, availableOptions, items} = subtitles;
    const text = srtStringify(items)
    return clearNotify(update(subtitles, {availableOptions: {[key]: {text: {$set: text}}}}));
  });
}