add UseTransformer
minor #915 add UseTransformer (keradus)

This PR was squashed before being merged into the 2.0-dev branch (closes #915).

Discussion
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add UseTransformer

add UseTransformer

Resolve #896

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

Commits
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febadf5 add UseTransformer