Cannot get rest parameters in katalon 5.4.2

Hi team, I use Katalon 5.4.2 and I’m doing a Restful web service test. I have made web service request object where I assigned some parameters. In the test case script, I want to get the parameters that I’ve put in the object by using getRestParameters(). I expected that it will returned the list of parameters that i’ve put, but i got a blank list.
Here’s the example
Do you have any solution how to get the parameters? Thank you and hope someone can answer it soon.