set_state() not working in walker

Hello,

I believe the `set_state()` function does not work for the walker environment.
The walker environment (https://github.com/deepmind/dm_control/blob/main/dm_control/suite/walker.py) defines its own Physics class, that extends the mujoco.Physics class, but does not extend the set_state() function.
I tried implementing the extra functions needed on my own but I believe I would need to build the repo, and that is not possible.
Am I missing something?
If not, can the extra functionality be added?

Start with dm_control/suite/walker.py and compare its Physics class with mujoco.Physics, focusing on the inherited set_state() behavior. Confirm whether walker-specific state needs handling and identify the repository's existing build or verification path; done means set_state() works for the walker environment without breaking its physics state.

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