add string implementation, can handle partial string slices

finish core implementation, added Index object

fix up the logic

add in new SliceOption object, cleaning up tests

Merge pull request !6192 from lijiaqi/sequentialcell

Merge pull request !6155 from byweng/master

Merge pull request !6142 from xiefangqi/md_fix_map_issue

Merge pull request !6002 from BowenK/pre_ad

Merge pull request !5753 from lijiaqi/loss_scale_sens

Merge pull request !6020 from XunDeng/new_check_param

Merge pull request !6108 from hanyang/master

Merge pull request !6032 from vlne-v1/change_ops_import

Merge pull request !6069 from zhangbuxue/support_function_as_condition_of_if

Merge pull request !5842 from luoyang/pylint

Merge pull request !6086 from ZiruiWu/order_dict_in_create_dict_iterator

fix CI

Merge pull request !5801 from xiefangqi/md_modify_output_tensor

Merge pull request !4950 from anthonyaje/monitor_fix

Merge pull request !6026 from suteng/master

Merge pull request !6019 from nhussain/move_random_choice_apply

Merge pull request !5735 from caozhou/delete_seed

Merge pull request !5998 from yihuaijie/master

Merge pull request !5929 from MahdiRahmaniHanzaki/bucket_batch_by_length_fix

Merge pull request !5958 from lilei/modify_bug

Merge pull request !5991 from yihuaijie/master

ci fix 1

fix ci 2

fix ci 3

fix ci 4

fix ci 5

fix ci 6

fix ci 7

change var name in CelebA from dataset_type to usage

address review cmts

fix cpp ut fail

change mode to usage in VOCDataset

fix cmts

fix ci test case fail

Merge pull request !5885 from vlne-v1/add-doc-for-composite-op

Merge pull request !5806 from xiefangqi/md_delete_setdatasetsize

Merge pull request !5749 from amongo/SupportPyantiveMultiGrad