GitLab

* add inference example to LayoutLMv2ForQuestionAnswering, passing doctest

* add loss example to LayoutLMv2ForQuestionAnswering, passing doctest

* Add correct doctest for LayoutLMv2ForTokenClassification, passing doctest

* add correct doctest for LayoutLMv2ForSequenceClassification, passing test

* add correct doctest for LayoutLMv2Model, passing test

* make fixup

* fix to address review comments

* make style

* fix doctest line break issue, add to documentaiton_tests.txt, address review comments

* move comment about layoutlmv2 dependencies to the doc page

* format doc page as suggested
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* delete extraneous backtick
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>