Text API (Resubmit #8763 #9394)

[szha]

Description

This is resubmission of #8763 #9394 @astonzhang

Checklist

Essentials

• Passed code style checking (make lint)
• 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
• To the my best knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change

Changes

• Resubmit Add mxnet.text APIs #8763 text api changes #9394
• Move to contrib

[szha]

This is one minor additional change to avoid changing the mxnet import chain in __init__

[piiswrong]

I think this is more commonly called Vocabulary

[piiswrong]

I'll do a pass some time soon. API naming and interfaces need to be changed.
@astonzhang would you like to do the resubmission or would you like @szha to handle it?

[szha]

@piiswrong I submitted this PR for respecting your request to move the text API to contrib. Given that the original PR has spanned a month, and you commented on it, I was under the impression that you had plenty of time to provide feedback on it. That said, let's address your concerns step-by-step.

Since @astonzhang has iterated with me on this over quite some time in #8763, there would be lots of context to help explain the motivation behind the design, on which Aston and I are happy to fill you in.

Then, if you still think that API changes need to be done, I agree with @mli that if you would propose the desired changes through an email thread on dev-list, issues, or through a new PR proposal, it would be much preferred. Besides, I look forward to learning the more desirable design from you. Thank you very much.