[DOC] Adding documentation to xlnet scripts

[zburning]

Description

Adding doc to xlnet scripts

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

cc @dmlc/gluon-nlp-team

[codecov]

Codecov Report

Merging #985 into master will increase coverage by 8.18%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #985      +/-   ##
==========================================
+ Coverage   81.49%   89.67%   +8.18%     
==========================================
  Files          67       67              
  Lines        6392     6392              
==========================================
+ Hits         5209     5732     +523     
+ Misses       1183      660     -523

Impacted Files	Coverage Δ
src/gluonnlp/utils/files.py	45.09% <0%> (-3.93%)	⬇️
src/gluonnlp/data/glue.py	98.63% <0%> (+1.81%)	⬆️
src/gluonnlp/model/train/embedding.py	87.17% <0%> (+2.56%)	⬆️
src/gluonnlp/embedding/token_embedding.py	92.01% <0%> (+2.83%)	⬆️
src/gluonnlp/vocab/elmo.py	96.66% <0%> (+3.33%)	⬆️
src/gluonnlp/data/word_embedding_evaluation.py	92.39% <0%> (+3.42%)	⬆️
src/gluonnlp/data/registry.py	78.12% <0%> (+6.25%)	⬆️
src/gluonnlp/data/stream.py	84.97% <0%> (+7.25%)	⬆️
src/gluonnlp/model/utils.py	77.58% <0%> (+7.75%)	⬆️
src/gluonnlp/model/transformer.py	90.76% <0%> (+8.97%)	⬆️
... and 10 more

[mli]

Job PR-985/1 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-985/1/index.html

[mli]

Job PR-985/2 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-985/2/index.html

[leezu]

Thanks @zburning! The linting step is still currently still failing (see http://ci.mxnet.io/blue/organizations/jenkins/GluonNLP-py3-master-gpu-integration/detail/PR-985/2/pipeline#step-68-log-1133 )
Could you help to fix it?

For running lint locally, execute pylint --rcfile .pylintrc PATH_TO_FILES_TO_CHECK. To install all optional and development dependencies of GluonNLP, you can run cd GLUONNLP; pip install -e '.[extras,dev]'. The development dependencies include everything needed to run the linting.

[mli]

Job PR-985/3 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-985/3/index.html

[leezu]

default is None

[leezu]

Should be ParameterDict or None

[mli]

Job PR-985/4 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-985/4/index.html

[mli]

Job PR-985/5 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-985/5/index.html

[leezu]

Thank you!