* hide misc APIs

* update

* fix transformer test

* update API.spec

Fix str and bytes problem
Fix sorted problem
Fix math problem
Fix CI problem

* remove block api

* remove clone_variable

* hide block inner apis

* update

* fix tests

* change return_numpy[PE] default value

* Remove convert to numpy in unit test

replace use_event with use_cuda, because use_event means the program running with CUDA, so use_cuda maybe more intuitive.