code: func (d *Document) FleschReadingEase() float64 {
  	x := 1.015 * d.NumWords / d.NumSentences
  	y := 84.6 * d.NumSyllables / d.NumWords
  	return 206.835 - x - y
  }
docs: // FleschReadingEase computes the Flesch reading-ease score
  // (https://en.wikipedia.org/wiki/Flesch%E2%80%93Kincaid_readability_tests).