anchor.diff:  
         // Make room for the allowed help.
         if (option.allowedHelp != null) {
  -        for (var allowed in option.allowedHelp.getKeys()) {
  +        for (var allowed in option.allowedHelp.keys) {
             title = max(title, getAllowedTitle(allowed).length);
           }
         }
  
positive.code:   }
  
    /** Get the names of the options as a [Collection]. */
    Collection<String> get options => _options.getKeys();
  }
  
  class _Option {
  
negative.code:    * that abbreviation.
     */
    _Option _findByAbbr(String abbr) {
      for (var option in _options.values) {
        if (option.abbreviation == abbr) return option;
      }
  
  