code: func (rank *Rank) UpdateWord(word string, prevWordIdx int, sentenceID int) (wordID int) {
  	wordID = rank.WordValID[word]
  
  	found := false
  
  	for _, oldSentenceID := range rank.Words[wordID].SentenceIDs {
  		if sentenceID == oldSentenceID {
  			found = true
  			break
  		}
  	}
  
  	if !found {
  		rank.Words[wordID].SentenceIDs = append(
  			rank.Words[wordID].SentenceIDs,
  			sentenceID,
  		)
  	}
  
  	rank.Words[wordID].Qty++
  
  	if prevWordIdx >= 0 {
  		rank.Words[wordID].ConnectionLeft[prevWordIdx]++
  	}
  
  	return
  }
docs: // UpdateWord method update a word what already exists in the rank object. It
  // retrieves its ID.