Bug: NameError: name 'PeftModel' is not defined due to unguarded reference

[fkarg]

In version 0.7.1 (latest at time of writing), it is inevitable to get a NameError upon usage of the SFTTrainer.

Occurances of PeftModel, such as

trl/trl/trainer/sft_trainer.py

Line 141 in 34e6948

if not isinstance(model, PeftModel):

are normally guarded by is_peft_available, e.g.:

trl/trl/trainer/sft_trainer.py

Line 134 in 34e6948

if is_peft_available() and peft_config is not None:

However, this is not the case here:

trl/trl/trainer/sft_trainer.py

Line 154 in 34e6948

elif not isinstance(model, (PreTrainedModel, PeftModel)):

As such, it is not available and thus (correctly) not imported where the unguarded reference correctly causes a NameError.

[fkarg]

(Will be fixed by #668)

(Issues related: #667 #601 and probably others)