code: func (rs *Ruleset) Singularize(word string) string {
  	if len(word) == 0 {
  		return word
  	}
  	if rs.isUncountable(word) {
  		return word
  	}
  	for _, rule := range rs.singulars {
  		if rule.exact {
  			if word == rule.suffix {
  				return rule.replacement
  			}
  		} else {
  			if strings.HasSuffix(word, rule.suffix) {
  				return replaceLast(word, rule.suffix, rule.replacement)
  			}
  		}
  	}
  	return word
  }
docs: // returns the singular form of a plural word