Add simple class to ease saving loading from HF hub

Would like to have a class from which model class can be inherited to add support of Huggingface hub. It will look something like this :

from huggingface_hub import SavingUtils

class MyModel(nn.Module, SavingUtils):

   def __init__(self):
      self.layer1 = ....

   def forward(self, ...):
      return ...

model = MyModel()
model.save_pretrained("model_id")

# loading model
model = MyModel.from_pretrained("model_id")

I can make a PR for adding this simple feature if you approve it.

[sgugger]

I agree with @julien-c and @patrickvonplaten on the fact it should be a mixin. Seems like a useful feature, so thanks for tackling this @vasudevgupta7 !

[patrickvonplaten]

I’m fine with adding a .upload_to_hub() method in PreTrainedModel(....) next to save_pretrained(...) and from_pretrained(...) - I don’t think we really need a new Mixin class for that