AttributeError while creating Brax Systems

[brn-dev]

I wanted to try out your colab notebooks (e.g. https://colab.research.google.com/github/google/brax/blob/main/notebooks/basics.ipynb#scrollTo=7GhvlPFTCbuq), but when I'm executing the second cell where Brax Systems are created I get the following error:

/usr/local/lib/python3.10/dist-packages/brax/io/mjcf.py in loads(xml, asset_path)
523 mj = mujoco.MjModel.from_xml_string(xml, assets=assets)
524
--> 525 return load_model(mj)
526
527

/usr/local/lib/python3.10/dist-packages/brax/io/mjcf.py in load_model(mj)
269 if (mj.geom_priority[0] != mj.geom_priority).any():
270 raise NotImplementedError('geom_priority parameter not supported.')
--> 271 if mj.opt.collision == 1:
272 raise NotImplementedError('Predefined collisions not supported.')
273 q_width = {0: 7, 1: 4, 2: 1, 3: 1}

AttributeError: 'mujoco._structs.MjOption' object has no attribute 'collision'

The collision attribute was removed in this commit of mujoco:
google-deepmind/mujoco@9cf1f6e

Is there a workaround to fix this error?

[brn-dev]

The offending line can be found here: https://github.com/google/brax/blob/main/brax/io/mjcf.py#L271

Can it simply be removed now, since the attribute doesn't exist anymore and it would only raise an error anyway?

If it can be removed: #411

[btaba]

Thanks @brn-dev for the fix!