ENH: Add attribute to show targeted module names

[BenjaminBossan]

This is just a tiny convenience feature to help users understand which modules are being targeted by the adapter. This can be useful to quickly check if a complex regex works for target_modules.

Note: This should work for all adapters that use BaseTuner, so not only LoRA but also IA³, LoHa, etc. Only the first two were tested but that should be enough.

Usage:

config = LoraConfig(target_modules=<COMPLICATED-REGEX>)
model = get_peft_mode(base_model, config)
print(model.targeted_module_names)

[HuggingFaceDocBuilderDev]

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[pacman100]

Thank you @BenjaminBossan for adding this feature to see all the targeted module names, LGTM!