* Fix save crash for legacy list-form _tied_weights_keys (NemotronH)
transformers >= 5 save_pretrained reads module._tied_weights_keys.keys(),
which raises 'list' object has no attribute 'keys' for modules that still
declare the attribute as a list (e.g. NemotronH backbone.layers.N.mixer.*_proj),
crashing GGUF export and merged saves part-way through.
Coerce any legacy list/tuple _tied_weights_keys into the dict form transformers
5.x expects, mapping each key to itself. Only the keys are read (as dedup
patterns) so behaviour is preserved, and older transformers that iterate the
attribute directly see the same keys. The helper is idempotent and best-effort
so a save never fails over it. Called from unsloth_save_model,
unsloth_save_pretrained_gguf and unsloth_generic_save after tokenizer patching.
Adds version-independent unit tests covering list/tuple coercion, dict and
None/empty pass-through, idempotency and odd-object tolerance.
* Coerce empty/set _tied_weights_keys too
transformers only skips _tied_weights_keys when it is None, so an empty list,
tuple or set still reaches .keys() and raises the same AttributeError. Coerce
every non-dict container (including the empty case and sets) to a dict, and add
tests for empty/set inputs.
* Tighten comments in tied-weights save fix
* Scope tied-weights-keys coercion to the save call
Coercing legacy list-form _tied_weights_keys to {k: k} fixed the transformers
5 save crash, but persisted a self-mapping on the live model. transformers 5
re-ties from the dict's values, so a later resize/re-tie would no-op the tie
instead of pointing the output weights back at the input embeddings.
Replace the in-place mutation with a decorator that coerces before the save and
restores the originals afterwards (including on exception), so the save sees the
dict form transformers needs while the model keeps its original tie metadata.
* [pre-commit.ci] auto fixes from pre-commit.com hooks
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* Trim comments to be more succinct
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Co-authored-by: Daniel Han <michaelhan2050@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
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