public default Object createIdleDetectionMessage() {
        return null;
    }
Create a message to send to seemingly dead clients to see if they respond back. The message sent will be
dependent on the implementation. For example, a websocket implementation would create a "ping" message.
This method will only be used if {@link #supportsIdleMonitor()} is {@code true}.
gremlin-server/src/main/java/org/apache/tinkerpop/gremlin/server/Channelizer.java