-replace switch'case by indexing

- Add test case
- Add constructors
- Add getItem string

- Fix bugs
- Add more tests

- Tensor iterator
- asNumpy
- TextFileDataset

- Tensor(Numpy)

- Super > 2D
- Add more test cases for GeneratorDataset

- Change StartAddr to GetBuffer and GetMutableNuffer

- Raise an error if batch is used with strings

Clean-up work

Merge pull request !1157 from ms_yan/concat_dataset

Merge pull request !1126 from xiefangqi/voc_support_detection

change to use __add__ operation instead ds.concat

Merge pull request !1139 from JesseKLee/timing_hole

Merge pull request !1131 from xulei/filter_op

support for 1 specific dimension to be None, added validator

fix various CI complains

another round of CI fixes

ci

refactor parts of the code

code refactor

ci fix

comments added, fix bugs

address review comments

address review comments

review cmts

added simple perf test script

update pad code

perf imprv

Merge pull request !869 from JesseKLee/random_data_op

Merge pull request !856 from jiangzhiwen/dataset/skip_thread

Merge pull request !406 from Peilin/first-row-crc-check

addressed code review comments. added check in python layer to exclude directories and to raise an error if a pattern does not match any file

fixed clang format

fixed cppcheck

fixed cppcheck (used std::accumulate and std::copy_if). regenerated tfrecord file to contain correct header, it was a dummy header before

fixed cppcheck: added const reference for string parameter for lambdas, fixed clang format: whitespace adjustments

more clang whitespace fixes...

changed print to logger.info

Merge pull request !425 from yanghaitao/yht_textfiledatasetv2

Merge pull request !183 from JunhanHu/cpp_sampler

Merge pull request !168 from Alexey_Shevlyakov/remove_mindspore_make_unique

Signed-off-by: Jonathan Yan <jonathan.yan1@huawei.com>

Signed-off-by: leonwanghui <leon.wanghui@huawei.com>