public String toString(){
    if (toRender==null)
      return null;
    else
    if (toRender instanceof Appender){
      StringBuffer sb=new StringBuffer();
      try {
        ((Appender)toRender).appendTo(sb);
      } catch (java.io.IOException e) {
        throw new RuntimeException(e);
      }
      return sb.toString();
    }
    else 
      return toRender.toString();
  }