docs: protected String describeAttribute(MBeanAttributeInfo attr) {
          StringBuilder buf = new StringBuilder();
          buf.append("(");
          if (attr.isReadable()) {
              buf.append("r");
          }
          if (attr.isWritable()) {
              buf.append("w");
          }
          buf.append(") ")
                  .append(attr.getType())
                  .append(" ")
                  .append(attr.getName());
          return buf.toString();
      }