code: private final String prefix(String style) {
          InternalStringBuilder sb = new InternalStringBuilder(16);
          sb.append(_stylePrefix);
          if(style != null) {
              sb.append(DELIM);
              sb.append(style);
          }
          return sb.toString();
      }
docs: Utility method to concatenate the given style class name and the style prefix.
  @param style the core style name
  @return the style class