Failed to import Rope in hello_world

Hi everyone,i read this tutorial. (4. Adding a Manipulator Robot — Omniverse Robotics documentation) The robotic arm gripping a cube. But i want to create a rope in this scene. The rope is composed of several capsule-shaped rigid bodies with joints. The 3d model can be found at the following path: /.local/share/ov/pkg/isaac_sim-2022.2.0/kit/extsPhysics/omni.physx.demos-104.1.6-5.1/omni/physxdemos/scenes
or in the Isaac sim - window - simulation - demo scenes - Joints - Rigid-Body Ropes

My questions are:

  1. I added the code from Rigid-Body Ropes to the hello world, but nothing happens. I noticed that the added code about creating the ropes is not being called, which means they are invalid. But they work well in the demo file. I want to know why.
  2. I just try to call them after adding, but i always fail. Hope someone can give me some advice

my file: (10.9 KB)

following are the errors:

2023-02-23 13:49:06 [Error] [asyncio] Task exception was never retrieved
2023-02-23 13:49:06 [Error] [asyncio] future: <Task finished coro=<BaseSampleExtension.on_load_world..on_load_world_async() done, defined at /home/student2/.local/share/ov/pkg/isaac_sim-2022.2.0/exts/omni.isaac.examples/omni/isaac/examples/base_sample/> exception=ErrorException(Error in 'pxrInternal_v0_20__pxrReserved::UsdStage::_IsValidPathForCreatingPrim’ at line 3258 in file /buildAgent/work/ca6c508eae419cf8/USD/pxr/usd/usd/stage.cpp : ‘Path must be an absolute path: <>’)>
2023-02-23 13:49:06 [Error] [asyncio] Traceback (most recent call last):
2023-02-23 13:49:06 [Error] [asyncio] File “/home/student2/.local/share/ov/pkg/isaac_sim-2022.2.0/exts/omni.isaac.examples/omni/isaac/examples/base_sample/”, line 150, in _on_load_world_async
2023-02-23 13:49:06 [Error] [asyncio] await self._sample.load_world_async()
2023-02-23 13:49:06 [Error] [asyncio] File “/home/student2/.local/share/ov/pkg/isaac_sim-2022.2.0/exts/omni.isaac.examples/omni/isaac/examples/base_sample/”, line 47, in load_world_async
2023-02-23 13:49:06 [Error] [asyncio] await self._world.reset_async()
2023-02-23 13:49:06 [Error] [asyncio] File “/home/student2/.local/share/ov/pkg/isaac_sim-2022.2.0/exts/omni.isaac.core/omni/isaac/core/world/”, line 307, in reset_async
2023-02-23 13:49:06 [Error] [asyncio] task.set_up_scene(self.scene)
2023-02-23 13:49:06 [Error] [asyncio] File “/home/student2/.local/share/ov/pkg/isaac_sim-2022.2.0/exts/omni.isaac.examples/omni/isaac/examples/hello_world/”, line 177, in set_up_scene
2023-02-23 13:49:06 [Error] [asyncio] self.create(self.stage1)
2023-02-23 13:49:06 [Error] [asyncio] File “/home/student2/.local/share/ov/pkg/isaac_sim-2022.2.0/exts/omni.isaac.examples/omni/isaac/examples/hello_world/”, line 50, in create
2023-02-23 13:49:06 [Error] [asyncio] UsdShade.Material.Define(self.stage, self.physicsMaterialPath)
2023-02-23 13:49:06 [Error] [asyncio] pxr.Tf.ErrorException:
2023-02-23 13:49:06 [Error] [asyncio] Error in 'pxrInternal_v0_20__pxrReserved
::UsdStage::_IsValidPathForCreatingPrim’ at line 3258 in file /buildAgent/work/ca6c508eae419cf8/USD/pxr/usd/usd/stage.cpp : ‘Path must be an absolute path: <>’

Thanks a lot!