We should not be returning an any type... this ruins all of the work you've done elsewhere in the file.

You would have the same effect if you replaced this whole file with this:

function getSegmenter(): any {
  return new Intl.Segmenter('eng', { granularity: 'word' });
}

Did you try using Segmenter instead of any here? Perhaps you tried that but got some Flow errors? We should try to resolve those errors.