* [CodeStyle] remove all future import

* revert test_error.py

* restore future import in example code

* use yapf to format all python file

* yapf exclude two unittests file for they rely on writing and reading file, and format will break them

* disable diff_py_file because too many diff files cause command following failed

* support construct scalar using non-cpu tensor

* fix bugs when run unittest

* fix compile bugs

* fix bugs when run ci

* fix compile bugs

* fix bugs when move copy

* perfect unit test

* perfect unittest

* update according to comment

* int_array supports constructed by gpu tensor

* add some test

* polish code

* adjust full api

* add unittest

* add unittest
Co-authored-by: NYuanRisheng <yuanrisheng@baidu.com>