How to export the sim env to usda?

Hi~ Thanks for the great work Isaacgym! I am playing with the demo Ant.
I’m just curious how can we export the scene we build in isaacgym? By “export the scene”, I mean I would like to export all the meshes imported at the beginning.
I tried to export the sim using:

        usda_exporter = self.gym.create_usd_exporter()
        self.gym.set_usd_export_root(usda_exporter, "./export")
        self.gym.export_usd_sim(usda_exporter,  self.sim, "scene", "export")

But got the ground plane only:

And if I import some mesh assets e.g., ‘/media/frank/easystore/_Proj/isaacgym/IsaacGymEnvs/assets/urdf/ycb/011_banana/011_banana.urdf’ and try to export them, I will get something like this: