Python warnings found in code output

[github-actions]

Python Warnings Detected

🚨 12 Python warning(s) were found in the HTML output during the documentation build.

Details:

• Repository: QuantEcon/lecture-python.myst
• Workflow: Build Project [using jupyter-book]
• Run ID: 17005333113
• Commit: 7638258
• Branch: 529/merge
• Date: 2025-08-16T06:53:22.209Z

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RuntimeWarning in ./_build/html/back_prop.html

Found 2 instance(s):

1:/home/runner/miniconda3/envs/quantecon/lib/python3.12/pty.py:95: RuntimeWarning: os.fork() was called. os.fork() is incompatible with multithreaded code, and JAX is multithreaded, so this will likely lead to a deadlock.
  pid, fd = os.forkpty()

RuntimeWarning in ./_build/html/two_auctions.html

Found 8 instance(s):

6:/tmp/ipykernel_8932/521884726.py:25: RuntimeWarning: Mean of empty slice.
  return array_conditional[-order,:].mean()
/home/runner/miniconda3/envs/quantecon/lib/python3.12/site-packages/numpy/core/_methods.py:129: RuntimeWarning: invalid value encountered in scalar divide
  ret = ret.dtype.type(ret / rcount)
6:/tmp/ipykernel_8932/919518230.py:37: RuntimeWarning: Mean of empty slice.
  return array_conditional[-order,:].mean()
/home/runner/miniconda3/envs/quantecon/lib/python3.12/site-packages/numpy/core/_methods.py:129: RuntimeWarning: invalid value encountered in scalar divide
  ret = ret.dtype.type(ret / rcount)

RuntimeWarning in ./_build/html/status.html

Found 2 instance(s):

1:/home/runner/miniconda3/envs/quantecon/lib/python3.12/pty.py:95: RuntimeWarning: os.fork() was called. os.fork() is incompatible with multithreaded code, and JAX is multithreaded, so this will likely lead to a deadlock.
  pid, fd = os.forkpty()

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Next Steps:

1. Review the warnings listed above
2. Fix the underlying code that's generating these warnings
3. Re-run the build to verify the warnings are resolved

Note: This issue was automatically created by the Check for Python Warnings Action.

Please close this issue once all warnings have been addressed.

[mmcky]

Closing as duplicate of #550