Allow for export ONNX model with dict inputs

[natuan]

This allows for passing in inputs of dict type to the export_onnx, enabling exported model with the original inp/out names.

[bfineran]

LGTM overall, I'm worried that for models with multiple inputs, the proper input order will not be preserved by a Dict unless it is an OrderedDict.

It might be safer to have input_names as a separate arg whose names should match the order of the sample input. Having a warning if the Dict is not ordered might also be ok though. If we keep Dict the transformers integration should be updated to use an ordered one.

[natuan]

LGTM overall, I'm worried that for models with multiple inputs, the proper input order will not be preserved by a Dict unless it is an OrderedDict.

It might be safer to have input_names as a separate arg whose names should match the order of the sample input. Having a warning if the Dict is not ordered might also be ok though. If we keep Dict the transformers integration should be updated to use an ordered one.

Added the followings:

• Warning if sample batch passed in is a dict but not an ordered dict
• From transformers side, the sample batch constructed as OrderedDict

[bfineran]

LGTM, thanks @natuan!

[bfineran]

looks like quality needs to run @natuan