code: protected String pluralizeInternal(String word) {
      for (Rule rule : rules) {
        if (rule.applies(word)) { return rule.apply(word); }
      }
      return null;
    }
docs: <p>
  Goes through the rules in turn until a match is found at which point the rule is applied and
  the result returned. If no rule matches, returns <code>null</code>.
  </p>
  
  @param word
  a singular noun
  @return the plural form of the noun, or <code>null</code> if no rule
  matches