[DOC] Cite source of pretrained parameters for bert_12_768_12

[leezu]

Description

Cite source of pretrained parameters for bert_12_768_12 in docstring and on modelzoo.

Fixes #896

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

• Cite source of pretrained parameters for bert_12_768_12

Comments

• @eric-haibin-lin

[codecov]

Codecov Report

❗ No coverage uploaded for pull request head (citebertmodels@547928b). Click here to learn what that means.
The diff coverage is n/a.

[codecov]

Codecov Report

Merging #915 into master will increase coverage by 17.06%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master     #915       +/-   ##
===========================================
+ Coverage   72.87%   89.93%   +17.06%     
===========================================
  Files          66       66               
  Lines        6400     6400               
===========================================
+ Hits         4664     5756     +1092     
+ Misses       1736      644     -1092

Impacted Files	Coverage Δ
src/gluonnlp/model/bert.py	99.45% <ø> (+50.27%)	⬆️
src/gluonnlp/data/question_answering.py	100% <0%> (+1.66%)	⬆️
src/gluonnlp/model/train/embedding.py	87.26% <0%> (+2.54%)	⬆️
src/gluonnlp/vocab/elmo.py	96.66% <0%> (+3.33%)	⬆️
src/gluonnlp/embedding/token_embedding.py	92.01% <0%> (+5.67%)	⬆️
src/gluonnlp/data/stream.py	85.05% <0%> (+7.21%)	⬆️
src/gluonnlp/model/utils.py	77.58% <0%> (+7.75%)	⬆️
src/gluonnlp/data/dataset.py	97.61% <0%> (+10.31%)	⬆️
src/gluonnlp/model/transformer.py	91.2% <0%> (+10.55%)	⬆️
src/gluonnlp/data/registry.py	78.12% <0%> (+12.5%)	⬆️
... and 15 more

[mli]

Job PR-915/1 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-915/1/index.html

[leezu]

Don't merge yet, turns out there is some issue with the links on the http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-915/1/model_zoo/bert/index.html

[leezu]

Should be good now

[mli]

Job PR-915/2 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-915/2/index.html