* [CodeStyle] remove all future import

* revert test_error.py

* restore future import in example code

* use yapf to format all python file

* yapf exclude two unittests file for they rely on writing and reading file, and format will break them

* disable diff_py_file because too many diff files cause command following failed

* fix error; test=develop

* update

* close some yaml

* fix backward attrite error; test=develop

* add div test

* polish code; test=develop

* update

* update

* fix bug

* update bitwise code; test=develop

* update

* update

* fix some bug

* update

* revert cmakelist

* fix optional bug;

* fix bug

* fix bug;

* add backward test

* open bn

* update

* update

* revert eager_gen

* polish code

* fix topk error

* update

* update

* fix bug;

* move label smooth, nll loss

* revert topk

* fix topk label smooth bug;

* remove batch_norm

* remove topk

* change flip infer meta

* fix flip bug

* update yaml

* close abs

* fix histogram bug

* fix histogram bug

* add abs

* fix histogram kernel

* remove expand

* 1. add the python api grad 2. add final and intermediate state vlog 3. change the python_api error logic

* add python api or close the check_eager=True

* fix the compatibility

* matmul

* disable unittests: test_elementwise_add_op test_scatter_nd_op test_gather_nd_op test_scatter_op test_index_sample_op test_elementwise_add_mkldnn_op

* add yolo box kernel; test=develop

* fix comile error; test=develop

* Enabled Eager OpTest #1

* Enabled Eager OpTest #1

* Fixed get_tensor method for EagerTensor

* add two attributes for yolo box

* alias yolo_loss & decode_yolo_box to paddle.vision. test=develop

* add scale_x_y for yolo_box, test=develop

* refine eps in iou_similarity, test=develop

* yolo_box OP add Attr(clip_bbox). test=develop

test=develop