Merge pull request !4787 from wenchunjiang/fix_code_check

Merge pull request !4746 from YuJianfeng/internal_output

Merge pull request !4795 from zyli2020/add_bn_fusion_pass

Merge pull request !4785 from TronZhang/fix_pass_release_bug

Merge pull request !4788 from zyli2020/gpu_bn_grad_perf_optimize

Merge pull request !4557 from caifubi/profiling

Merge pull request !4744 from lichen/support_bert

Merge pull request !4764 from zyli2020/gpu_bn_op_perf_optimize

Merge pull request !4689 from zhangbuxue/add_check_for_user_define_bprop_in_Pynative_mode

implment pause in MapOp, added more to callback

add ds_callback

- Initial drop of Python DSCallback

- Pybind DSCallback

- Pybind DSCallback

added callback to mapOp

- de_pipeline DSCallback

- de_pipeline DSCallback

add test case, segfault for now

fix seg fault

- de_pipeline DSCallback

remove 1 line

update callback test case, now works

use builder class for mapOp callback

- de_pipeline DSCallback

- de_pipeline DSCallback

- de_pipeline DSCallback

better test case

minor fix

add comments and minor clean ups

get rid of nullptr in MapOp, use other flag instead

fix a bug ParseMapOp only takes 1 callback

- Added WaitedDSCalabck

refactor callback param

fix text case incorrect number

- added testing

fix cpp test case

- added testing

- revert back lenet changes

- cleanup test_callbacks.py

- cleanup test_callbacks.py

fix CI stage I

fix CI stage II

fix CI and update epoch counter

- add validation
- add more testing  test_callbacks.py

use random data op to do tests

adjust when to call EpochBegin/End

- add repeat with callback

- addressing reviewers' comments

- docstring and CI fixes

- docstring and CI fixes

- docstring and CI fixes

- rebase with upstream/master

fix cpp test case

fix review comments

addr review cmts, add test case

Merge pull request !4759 from jiangzhiwen/dataset/fix_duplicate_column_names

Merge pull request !4685 from ZPaC/master-supports-export-server-ckpt

Merge pull request !4704 from chengang/fix_ps_multi_worker

Merge pull request !4696 from jiangzhiwen/jzw/c_api_csv

Merge pull request !4722 from lijiaqi/modify_error_type

Merge pull request !4622 from hexia/http_init

Merge pull request !4731 from gukecai/parallel-genmask

Merge pull request !4710 from xiefangqi/xfq_fix_tfreader_issue

Merge pull request !4498 from heleiwang/gnn_distributed

Merge pull request !4726 from 徐永飞/master

Merge pull request !4684 from 治愈系潇洒哥/master

Merge pull request !4715 from zhoufeng/xiu-ba-ge

Merge pull request !4690 from baihuawei/categorical

Merge pull request !4719 from xychow/fix-copyright-in-core

Merge pull request !4413 from caozhou/merge_parameter

Merge pull request !4723 from yangzhenzhang/concat-more-than-3-tensors

Merge pull request !4422 from xiefangqi/xfq_c++api_randomdata

Signed-off-by: zhoufeng <zhoufeng54@huawei.com>