I am not fully understanding your question. Could you describe a bit more clearly what your goal is?
Ah, I get what you mean now. But that is a very specific question to which I don't know the answer. Maybe you could open an issue at the repository? See: https://github.com/cisco-system-traffic-generator/trex-core/issues .
Ah, I see. I don't think he meant this forum, but rather their Google Group over here: https://groups.google.com/forum/#!forum/trex-tgn . You could try that, and otherwise I'd suggest waiting here and see if you can get a response here.