GitLab

* rename cacheable_method to cache_randomness

* refactor transform wrappers and update docs

* fix all_nonexist_keys

* fix lint

* rename transform wrappers

* Add data transfrom docs

* Convert all Chinese paragraph in oneline to prevent some rendering bug
in Chrome/Edge. (It looks well in Firefox :/)

* Update docs

* Update docs

* Imporve docs according to comments

* Imporve docs according comments