pickle5.pickle.PicklingError when import PSROScenario

[Xixo99]

After I following the readme.md, initialize the virtual environment and install the dependencies, try executing python examples/ run_pro.py, error occurs: pickle5.pickle.PicklingError: Could not pickle object as excessively deep recursion required.

Create a new py file in the folder and execute just one line of code. from malib.scenarios.psro_scenario import PSROScenario .
The same error message will appear. How can I solve this problem?