🐛 Fix multi-gpu error (AttributeError) for kongnet and nucleus_detector

[gozdeg]

Follow-up to the earlier multi-GPU fix. kongnet and nucleus_detector were missed and still crash on multi-GPU machines with:

AttributeError: 'DataParallel' object has no attribute 'target_channels'

When multi-gpu, the model is wrapped in nn.DataParallel / DistributedDataParallel, so these need to go through the _get_model_attr() wrapper helper function (or a similar approach) which unwraps the module before reading the attribute.

Changes

• nucleus_detector.py: read min_distance / tile_shape via the _get_model_attr helper instead of directly off self.model.
• kongnet.py: unwrap the module before reading target_channels in infer_batch. This can't reach the helper function, so it applies the same unwrap inline.
• engine_abc.py: simplify _get_model_attr to a single getattr-based unwrap and clarify its docstring.

[Copilot]

Pull request overview

This PR addresses a multi-GPU crash in TIAToolbox nucleus detection paths by ensuring model attributes are read safely when the model is wrapped by nn.DataParallel / DistributedDataParallel.

Changes:

• Update NucleusDetector.post_process_wsi to read min_distance and tile_shape via _get_model_attr() instead of directly from self.model.
• Update KongNet.infer_batch to resolve target_channels when model is wrapped, avoiding AttributeError under multi-GPU wrappers.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
tiatoolbox/models/engine/nucleus_detector.py	Uses the existing unwrapping helper to access model attributes under DP/DDP.
tiatoolbox/models/architecture/kongnet.py	Adds wrapper-aware access to target_channels so inference works under DP/DDP.

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[codecov]

Codecov Report

❌ Patch coverage is 71.42857% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 99.87%. Comparing base (c9c72c9) to head (186b27c).

Files with missing lines	Patch %	Lines
tiatoolbox/models/architecture/kongnet.py	60.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1074      +/-   ##
===========================================
- Coverage    99.88%   99.87%   -0.02%     
===========================================
  Files           85       85              
  Lines        11626    11630       +4     
  Branches      1524     1524              
===========================================
+ Hits         11613    11615       +2     
- Misses           7        9       +2     
  Partials         6        6              

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