Correct ONNX documentation

[vandanavk]

Description

Fixes #15437

Checklist

Essentials

Please feel free to remove inapplicable items for your PR.

• The PR title starts with [MXNET-$JIRA_ID], where $JIRA_ID refers to the relevant JIRA issue created (except PRs with tiny changes)
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage:
• Unit tests are added for small changes to verify correctness (e.g. adding a new operator)
• Nightly tests are added for complicated/long-running ones (e.g. changing distributed kvstore)
• Build tests will be added for build configuration changes (e.g. adding a new build option with NCCL)
• Code is well-documented:
• For user-facing API changes, API doc string has been updated.
• For new C++ functions in header files, their functionalities and arguments are documented.
• For new examples, README.md is added to explain the what the example does, the source of the dataset, expected performance on test set and reference to the original paper if applicable
• Check the API doc at http://mxnet-ci-doc.s3-accelerate.dualstack.amazonaws.com/PR-$PR_ID/$BUILD_ID/index.html
• To the my best knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change

Changes

• Refer the correct ONNX operator coverage doc
• Refer to the correct supported ONNX version

Comments

[vandanavk]

@mxnet-label-bot add [Doc, pr-awaiting-review]

[vandanavk]

@IvyBazan for review

[IvyBazan]

LGTM, thanks for the fix!
You may want to re-trigger CI

[vandanavk]

@aaronmarkham for review/merge

[aaronmarkham]

LGTM. But... can you also update the tutorial, or add that in another PR?
https://github.com/apache/incubator-mxnet/blob/master/docs/tutorials/onnx/export_mxnet_to_onnx.md
Or is the tutorial fine, and the version requirements fine?

[vandanavk]

LGTM. But... can you also update the tutorial, or add that in another PR?
https://github.com/apache/incubator-mxnet/blob/master/docs/tutorials/onnx/export_mxnet_to_onnx.md
Or is the tutorial fine, and the version requirements fine?

The tutorial was written with MXNet 1.3 and ONNX 1.2.1. Since the importer-exporter is backward compatible, this should still work and the statement "Note: MXNet-ONNX importer and exporter follows version 7 of ONNX operator set which comes with ONNX v1.2.1." holds true. Should I update the tutorial with information that MXNet now supports ONNX 1.3 with opset 8?

[aaronmarkham]

Since we have so much fun getting stuff through CI, let's merge this as is. Please add the extra info in another PR.

[IvyBazan]

LGTM