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* split the pre-processing functions in BRIE to another separate package
BRIE-kit, as some functions in the pre-processing require Python2 environment.
So, `BRIE` will keep two functions `brie` and `brie-diff`, while `BRIE-kit`
will have `briekit-event`, `briekit-event-filter`, and `briekit-factor`.
See BRIE-KIT: https://github.com/huangyh09/briekit/wiki