Is there a way to instantiate a Lightning Module class using a class method on Lightning CLI?

[carlesoctav]

Is there a way to instantiate a Lightning Module class using a class method on Lightning CLI? This problem arises when I try to create a model class that inherits from LightningModule and Huggingface's PretrainedModel Class. We all know that the PretrainedModel class uses the from_pretrained class method to instantiate a model loaded from the Huggingface hub. When I try to use LightningCLI, we all know that it will attempt to instantiate the instance with the init method.

[mauvilsa]

With jsonargparse v4.30.0 just released, now it is possible to give in class_path the import path of a method, like class_path: some.module.ClassName.method_name (see jsonargparse#513). But note, it is mandatory that the method have as return annotation the class type it returns. From what I have seen, this is not the case for Huggingface classes.

It will not be allowed to have functions without the return type annotation, because this would be vulnerability, since it would become possible to execute any function. But note, it shouldn't be too difficult to contribute required changes to transformers.

[mauvilsa]

Created this huggingface/transformers#31850

[mauvilsa]

Also created this pull request huggingface/transformers#31869. However, I tested the bert model and I am still getting the same error. Seems that this case is somehow different to the feature that I implemented. Not sure how. Will try to look at this tomorrow.

[carlesoctav]

Do you think the problem lies in how Lightning implemented the CLI? I've never tried using "raw" jsonargparse cli before to build my own CLI.

[mauvilsa]

I haven't had much time to look at this. I did notice that there is some logic in jsonargparse that normalizes import paths, and it is not working correctly for transformers.BertModel.from_pretrained. Could be that this is the only problem or there are more.

[mauvilsa]

I did find another issue with the parameter resolver. So, not yet ready to work with transformer models.