docs: protected String formatValue(List<Class<? extends C>> val) {
      StringBuilder buf = new StringBuilder(50 + val.size() * 25);
      String pkgname = restrictionClass.getPackage().getName();
      for(Class<? extends C> c : val) {
        if(buf.length() > 0) {
          buf.append(LIST_SEP);
        }
        String name = c.getName();
        boolean stripPrefix = name.length() > pkgname.length() && name.startsWith(pkgname) && name.charAt(pkgname.length()) == '.';
        buf.append(name, stripPrefix ? pkgname.length() + 1 : 0, name.length());
      }
      return buf.toString();
    }