@Override
  public Message getMessage(CacheClientProxy proxy, boolean notify) throws IOException {
    // the MessageDispatcher uses getMessage(CacheClientProxy, byte[]) for this class
    throw new Error("ClientUpdateMessage.getMessage(proxy) should not be invoked");
  }
Returns the unqiue event eventifier for event corresponding to this message.

@return the unqiue event eventifier for event corresponding to this message.
geode-core/src/main/java/org/apache/geode/internal/cache/tier/sockets/ClientUpdateMessageImpl.java