AutoModels for region-to-phrase-alignment and natural-language-for-visual-reasoning
### Feature request

Hi! Region to phrase alignment and natural language for visual reasoning have no AutoModels yet. @sgugger is it OK to open a PR and solve this?

### Motivation

This is an issue that I faced when exporting VisualBert to ONNX, since the task mapping can't be done without it. Adding it would allow us to make the export for every task.

### Your contribution

I'll open a PR and solve it myself if allowed
Note that the ONNX conversion is now done directly in the optimum library, so this is probably where you would need to add something.<|||||>That's true, I'm doing the ONNX conversion from optimum. But optimum references AutoModels directly from transformers. I'd just program the AutoModel subclasses without any optimum stuff, of course.<|||||>@sgugger Sorry for insisting, I know you have lots of issues opened already. Just tagging you to see if you still think this should be solved from Optimum<|||||>I think the optimum library should provide an API for models that don't have an auto API yes (if it does not already), as there will always be such models and we won't add a new auto class for just one model.

cc @michaelbenayoun who might have more information.<|||||>Hi @mszsorondo,
Could you open a PR on the Optimum repo, with your request explained please?<|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

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