fix code comment

[rongruosong]

Description

(Brief description on what this PR is about)

Checklist

Essentials

• PR's title starts with a category (e.g. [BUGFIX], [MODEL], [TUTORIAL], [FEATURE], [DOC], etc)
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage
• Code is well-documented

Changes

• Feature1, tests, (and when applicable, API doc)
• Feature2, tests, (and when applicable, API doc)

Comments

• If this change is a backward incompatible change, why must this change be made.
• Interesting edge cases to note here

[mli]

Job PR-656/1 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-656/1/index.html

[codecov]

Codecov Report

Merging #656 into master will increase coverage by 0.68%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #656      +/-   ##
==========================================
+ Coverage   63.04%   63.73%   +0.68%     
==========================================
  Files         151      141      -10     
  Lines       13779    12902     -877     
==========================================
- Hits         8687     8223     -464     
+ Misses       5092     4679     -413

Flag	Coverage Δ
#PR612	?
#PR656	63.73% <ø> (?)
#master	?
#notserial	42.62% <ø> (+2.73%)	⬆️
#py2	63.49% <ø> (-0.37%)	⬇️
#py3	63.61% <ø> (+0.68%)	⬆️
#serial	49.19% <ø> (-0.22%)	⬇️

[codecov]

Codecov Report

Merging #656 into master will increase coverage by 0.68%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #656      +/-   ##
==========================================
+ Coverage   63.04%   63.73%   +0.68%     
==========================================
  Files         151      141      -10     
  Lines       13779    12902     -877     
==========================================
- Hits         8687     8223     -464     
+ Misses       5092     4679     -413

Flag	Coverage Δ
#PR612	?
#PR656	63.73% <ø> (?)
#master	?
#notserial	42.62% <ø> (+2.73%)	⬆️
#py2	63.49% <ø> (-0.37%)	⬇️
#py3	63.61% <ø> (+0.68%)	⬆️
#serial	49.19% <ø> (-0.22%)	⬇️

[szha]

@rongruosong good catch. thank you for the fix

[astonzhang]

Thanks!