The keyword created by importing the third party jar package cannot be displayed in the "Custom Keywords"

I need to simulate the client sending a message under the MQTT protocol.
I did the following :
1、 Add third-party packages to “External Libraries”.

2、create a keywords.

3、Try calling the keyword

As shown in the last screenshot, there is no keyword I created: “clientSendMassage”, I need help, thank you.

def clientSendMessage(...) {

thank you .