[DOC] change the variable model to bert_classifier

[LindenLiu]

The "model" is a imported module from code section 1 and then overloaded on code section 4

model = model.classification.BERTClassifier(bert_base, num_classes=2, dropout=0.1)

This actually make this section not rerunable and if anything need to call the module "model", it will call the BERTClassifier object rather than the model imported in section 1. Propose to change the model to bert_classifier to avoid naming conflicts.

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]

Found link check problems in job PR-828/1:
(line 19) broken https://www.salesforce.com/products/einstein/ai-research/the-wikitext-dependency-language-modeling-dataset/ - 404 Client Error: Not Found for url: https://www.salesforce.com/products/einstein/ai-research/the-wikitext-dependency-language-modeling-dataset/
(line 5) broken https://www.salesforce.com/products/einstein/ai-research/the-wikitext-dependency-language-modeling-dataset/ - 404 Client Error: Not Found for url: https://www.salesforce.com/products/einstein/ai-research/the-wikitext-dependency-language-modeling-dataset/
(line 5) broken https://www.salesforce.com/products/einstein/ai-research/the-wikitext-dependency-language-modeling-dataset/ - 404 Client Error: Not Found for url: https://www.salesforce.com/products/einstein/ai-research/the-wikitext-dependency-language-modeling-dataset/
(line 21) broken https://www.salesforce.com/products/einstein/ai-research/the-wikitext-dependency-language-modeling-dataset/ - 404 Client Error: Not Found for url: https://www.salesforce.com/products/einstein/ai-research/the-wikitext-dependency-language-modeling-dataset/
(line 442) broken https://www.aclweb.org/anthology/P02-1040.pdf)[1 - 404 Client Error: Not Found for url: https://www.aclweb.org/anthology/P02-1040.pdf)%5B1
(line 92) broken https://nlp.stanford.edu/pubs/glove.pdf)[2 - 404 Client Error: NOT FOUND for url: https://nlp.stanford.edu/pubs/glove.pdf)%5B2
(line 208) broken https://www.bioinf.jku.at/publications/older/2604.pdf)[3 - 404 Client Error: Not Found for url: https://www.bioinf.jku.at/publications/older/2604.pdf)%5B3

[mli]

Job PR-828/1 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-828/1/index.html

[eric-haibin-lin]

Thanks for the fix!