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 !4422 from xiefangqi/xfq_c++api_randomdata

Merge pull request !4367 from MahdiRahmaniHanzaki/cutmix

Merge pull request !4322 from EricZ/bitmap_support

Merge pull request !3819 from jiangzhiwen/jzw/c_api_clue

Merge pull request !3771 from cathwong/ckw_c_api_textfile_nosampler

Merge pull request !3850 from islam_amin/randomaffine_op

Merge pull request !3917 from luoyang/c-api

split into datasets

review fix

fix merge issues

fixed minddata lite build issues

Added Distributed sampler option

Fix style

Added input check

Added SwapRedBlue

Merge pull request !2982 from ava/CPP_test3

fix cmakefile

fixed log statments in cpp UT tests

Merge pull request !2738 from islam_amin/object_ops_ut_cc

Removed extra fields in schema

Fixed test cases

Fixing CI

Merge pull request !2374 from MahdiRahmaniHanzaki/I1L892-pad-cutout-ut

init remove storage op test case c++

remove source c++ files

remove graphengine changes

concat op

Truncate Pair

concat_op

remove graph engine changes

Merge pull request !2028 from nhussain/fillOp_learning