code: public WikiFormat addStyle(WikiStyle style)
      {
          if (fStyles.contains(style)) {
              return this;
          }
          WikiFormat clone = getClone();
          clone.fStyles.add(style);
          return clone;
      }
docs: Creates a new style set and adds the given style to it.
  
  @param style the style to add
  @return a new copy of the style set containing the given style