* fix dataloader collate return list mix tensor and numpy array. test=develop

* remove numpy array check in single-process dataloader. test=develop

* set expected place in child thread for dataloader

* set device id when set tensor from numpy

* revert tensor_py change

* add compile guard

* fix ci

* fix bug

* upgrade comment string to raw string

* fix string in

* fix string with ' '

* revert update on comments

* upgrade only necessary

* fix sample code checker

* fix comments with '''

* DataLoader support not auto collate batch. test=develop

* fix DataLoader return same format between static & dynamic in single mode. test=develop

* fix dataloader

* fix DataLoader single process mode exit SIGABRT error. test=develop

* move worker loop to top level

* move reader process loop to top level

* fix failed unittests

* add TensorDataset. test=develop

* fix test_multiprocess_dataloader unittest. test=develop

* add IterableDataset support in multiprocess DataLoader. test=develop

* add pin memory control

* fix buffered reader init problem

* fix unittest error

* add unittest for coverage

* make default_collate_fn visible. test=develop

* fix test_multiprocess_dataloader_static random fail. test=develop

* add DataLoader, Dataset, BatchSampler