fix: add None guard for regex in load() and update addmm_() for PyTorch >= 2.0 compatibility

[SahilKumar75]

Problem

Two bugs in examples/MOT17/multiedge_inference_bench/pedestrian_tracking/testalgorithms/reid/m3l/basemodel.py that cause runtime failures:

1. load() — re.compile(...).search(model_url).group(1) raises AttributeError: 'NoneType' object has no attribute 'group' when the filename doesn't match the expected _<arch>.pth pattern.
2. _pairwise_distance() — dist_m.addmm_(1, -2, x, y.t()) uses the deprecated positional-float signature removed in PyTorch ≥ 2.0, raising TypeError.

Fix

• load(): capture the re.search() result and raise a descriptive ValueError if it's None, before calling .group(1).
• _pairwise_distance(): replace addmm_(1, -2, x, y.t()) with addmm_(x, y.t(), beta=1, alpha=-2), which is the correct keyword-argument form supported from PyTorch 1.5+ through 2.x.

Testing

Changes are logic-level; the regex fix is trivially verifiable and the addmm_ signature change matches the PyTorch ≥ 2.0 migration guide.

Fixes #445

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[gemini-code-assist]

Code Review

This pull request improves robustness in basemodel.py by escaping the dot in the regular expression and adding a safety check with a descriptive ValueError when parsing the model architecture from model_url. Additionally, it updates the addmm_ call to use keyword arguments for beta and alpha. The reviewer recommended converting model_url to a string before performing the regex search to prevent a potential TypeError if a pathlib.Path object is passed, and suggested using re.search directly instead of compiling.

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[gemini-code-assist]

If model_url is passed as a pathlib.Path object (which is highly possible given that Path(model_url) is used on line 70), re.search will raise a TypeError: expected string or bytes-like object. Converting model_url to a string first ensures robustness. Additionally, using re.search directly is more idiomatic than compiling a regex that is only used once.

Suggested change

	match = re.compile(r"_([a-zA-Z]+)\.pth").search(model_url)
	if match is None:
	raise ValueError(
	f"Cannot infer model architecture from filename: '{model_url}'. "
	"Expected format: '<name>_<arch>.pth'"
	)
	arch = match.group(1)
	model_url_str = str(model_url)
	match = re.search(r"_([a-zA-Z]+)\.pth", model_url_str)
	if match is None:
	raise ValueError(
	f"Cannot infer model architecture from filename: '{model_url_str}'. "
	"Expected format: '<name>_<arch>.pth'"
	)
	arch = match.group(1)

[SahilKumar75]

/assign @jaypume