docs: public void writeObjectInstance(OutputStream out, ObjectInstanceWrapper value) throws IOException {
          // ObjectInstance has no known sub-class.
          writeStartObject(out);
          writeObjectNameField(out, OM_OBJECTNAME, value.objectInstance.getObjectName());
          writeStringField(out, OM_CLASSNAME, value.objectInstance.getClassName());
          writeStringField(out, OM_URL, value.mbeanInfoURL);
          writeEndObject(out);
      }