2. fix test_graphdata_distributed.py failing randomly

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 !4498 from heleiwang/gnn_distributed

Merge pull request !4389 from yanghaitao/yht_fix_doc2

Merge pull request !4421 from ms_yan/api_comment

Merge pull request !4383 from genglishuai/genglshOK

Merge pull request !4366 from TinaMengtingZhang/cpp-api-repeat-count

Merge pull request !3651 from jiangzhiwen/dataset/change_num_samples

Merge pull request !3644 from liyong126/fix_mindrecord_bug

Merge pull request !3624 from yanghaitao/yht_generator_timeout

Merge pull request !3540 from liyong126/fix_mindrecord_log

Merge pull request !3532 from guansongsong/gss_fix_api

Merge pull request !3334 from ms_yan/device_que_param

Merge pull request !3318 from liyong126/fix_save_doc

Merge pull request !3328 from shenwei41/sw_master

Merge pull request !3093 from xiefangqi/md_voc_multi_columns

Merge pull request !3241 from panfengfeng/fix_some_log_error