GitLab

* Add ONNX support for ViT

* Refactor to use generic preprocessor

* Add vision dep to tests

* Extend ONNX slow tests to ViT

* Add dummy image generator

* Use model_type to determine modality

* Add deprecation warnings for tokenizer argument

* Add warning when overwriting the preprocessor

* Add optional args to docstrings

* Add minimum PyTorch version to OnnxConfig

* Refactor OnnxConfig class variables from CONSTANT_NAME to snake_case

* Add reasonable value for default atol
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>