Windows: parse/verify fail with timeout wrapper (AttributeError on local function pickling)

[rycerzes]

Summary

On Windows, math_verify.parse and math_verify.verify fail when timeout handling is enabled.
With default raise_on_error=False, failures are swallowed and parse returns [], which can
silently degrade correctness checks.

Environment

• OS: Windows 11
• Python: 3.13.3
• math-verify: 0.9.0

Minimal Repro

import math_verify

print(math_verify.parse(r"\\boxed{4}", raise_on_error=True))
print(math_verify.verify("4", "4", strict=True, timeout_seconds=1, raise_on_error=True))

Observed

AttributeError: Can't get local object 'timeout.<locals>.decorator.<locals>.wrapper.<locals>.run_func'

When raise_on_error=False (default):

• math_verify.parse(...) returns []
• math_verify.verify(...) returns False

Related symptom sometimes appears from multiprocessing teardown on Windows:

OSError: [WinError 6] The handle is invalid

Expected

• parse should return parsed candidates for valid boxed/math strings.
• verify("4", "4", ...) should return True.
• Timeout handling should work (or fail loudly with a clear platform-specific message), rather than
  silently returning empty parse results / false negatives.

Notes

The failure appears to be tied to the timeout implementation and Windows spawn multiprocessing,
where a local function used by the timeout wrapper is not picklable.