Bart Checklist (Completed):
- add model/configuration/tokenization classes
- add conversion scripts
- add tests
- finalize
- copy the python files from the present folder to the main folder and rename them, replacing xxx with your model name,
- edit the files to replace XXX (with various casing) with your model name
- copy-paste or create a simple configuration class for your model in the configuration_... file
- copy-paste or create the code for your model in the modeling_... files (PyTorch and TF 2.0)