add ArraySquareBraceTransformer
minor #916 add ArraySquareBraceTransformer (keradus)

This PR was squashed before being merged into the 2.0-dev branch (closes #916).

Discussion
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add ArraySquareBraceTransformer

add ArraySquareBraceTransformer

Resolve #913

- [X] tests
- [X] skeleton
- [x] implementation
- [x] update Tokenizer
- [X] update Fixers
- [x] rebase after merge of #917

Commits
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53a6ee1 add ArraySquareBraceTransformer