* add nms op and batched_nms api

* 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

* Use _C_ops.yolov3_loss in eager mode for test_yolov3.py

* fix code for test_yolov3_loss_op

* remove useless import

* Fix dygraph_mode flag

* refactor eager flags

* fix flags error when we switch from eager to dygraph

* fix ci problem

* fix ci

* fix ci

* merge develop and fix code style

* merge develop and fix code style

* fix op test error

* fix op test error

* fix op test error

* fix op test error

* fix op test error

* merge develop

* add mobilenetv3

* fix 'invalid escape sequence'

* fix assert error

* add roi_align in vision/ops.py

* add roi pool

* rename input as x

* add func/class API psroi_pool and UT

* add UT in static mode

* Remove redundant type checks in static mode

* More detailed description for test_psroi_pool_op

* fix code format of UT

* fix en-doc

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* fix warning error , test=document_fix

* cache core.ops, test=develop

* refine, test=develop

* update 2.0 public api in vision

* fix some flake8 errors

* add two attributes for yolo box

* add op read_file and decode_jpeg

* fixed docs.

* Fixed docs. test=document_fix

code bak.

fixed docs. test=document_fix

* Revert to previous version of python/paddle/fluid/backward.py

* fixed bugs.

* test=document_fix. Fixed examples.

* Support list and tuple for parameters of layer_norm, multiprocess_reader, DatasetFolder and ImageFolder.

* add unittest for layer_norm.

* add require gpu for example.

* add attrs deformable_groups

* add deform_conv2d,DeformConv2D

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