Wonderful work！ This issue is just a supplement for env form a follower.

[Looomo]

Wonderful work！ This issue is just a supplement for env form a follower.
numpy should use version 1.21.6, in case of module 'numpy' has no attribute 'int' error.
use free-mujoco-py instead of mujoco-py==2.0.2.13, as is described in the notebook file.

[ZhaoRunyi]

I use numpy version 1.21.6 to fix the module 'numpy' has no attribute 'int' error, while cause a ImportError: numpy.core.multiarray failed to import (auto-generated because you didn't call 'numpy.import_array()' after cimporting numpy; use '<void>numpy._import_array' to disable if you are certain you don't need it).error, and it seems due to the numpy version being too low. I wonder how can I fix it.