Import usd file as an articulation

[LouieTsai71]

Hi, I am doing a reinforcement learning project with isaac sim and isaac lab, and I am trying to modify the demo "arms.py" so that it can load my own usd file and move its joints. However the same modified code that worked for the usd files in the demo does not work for mine. Is there a specific way of structuring the usd? The following are my current scripts and usd file.
https://drive.google.com/file/d/1ntj2hiFV4TP_63Lo9SpoKPI_T6WnW1jQ/view?usp=sharing