* [CodeStyle] remove all future import

* revert test_error.py

* restore future import in example code

* [CustomDevice] add process_group_xccl ut

* update

* 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

* add pg_hccl

* add processgroup_nccl