* add isort config

* use isort to sort imports

* add isort to travis

* format the codebase with yapf

* add yapf to travis

* add reduction_override flag

* change default value of reduction_override as None

* add assertion, fix format

* delete redudant statement in util

* delete redudant comment

* Code for components of Libra R-CNN

* Configs and README for Libra R-CNN

* update bfp

* Update Model ZOO

* add comments in non-local

* fix shape

* update bfp

* update according to ck's comments

* update des

* update des

* fix loss

* fix according to ck's comments

* fix activation in non-local

* fix conv_mask in non-local

* fix conv_mask in non-local

* Remove outdated model urls

* refactoring for bfp

* change in_channels from list[int] to int

* refactoring for nonlocal

* udpate weight init of nonlocal

* minor fix

* update new model urls

* add two stage w/o neck and w/ upperneck

* add rpn r50 c4

* update c4 configs

* fix

* config update

* update config

* minor update

* mask rcnn support c4 train and test

* lr fix

* cascade support upper_neck

* add cascade c4 config

* update config

* update

* update res_layer to new interface

* refactoring

* c4 configs update

* refactoring

* update rpn_c4 config

* rename upper_neck as shared_head

* update

* update configs

* update

* update c4 configs

* update according to commits

* update

* add ga rpn

* test bug fix

* test bug fix with loc_filter_thr is large

* update configs

* update configs

* add ga_retinanet

* ga test bug fix

* update configs

* update

* init masked conv

* update

* update masked conv

* update

* support no ga_sampler

* update

* update

* test with masked_conv

* update comment

* fix flake errors

* fix flake 8 errors

* refactor bounded iou loss

* refactor ga_retina_head

* update configs

* refactor masked conv

* fix flake8 error

* refactor guided_anchor_head and ga_rpn_head

* update configs

* use_sigmoid_cls -> cls_sigmoid_loss; use_focal_loss -> cls_focal_loss

* refactoring

* cls_sigmoid_loss -> use_sigmoid_cls

* fix flake8 error

* add some docs

* rename normalize to norm_cfg

* update configs

* add readme

* update ga_faster config

* update readme

* update readme

* rename configs as r50_caffe

* merge master

* refactor guided anchor target

* update readme

* update approx mas iou assigner

* refactor guided anchor target

* update docstring

* refactor ga heads

* fix flake8 error

* update readme

* update model url

* update comments

* refactor get anchors

* update docstring

* not use_loc_filter during training

* add R-101 results

* update to support build loss api

* fix flake8 error

* update readme with x-101 performances

* update readme

* add a link in project readme

* refactor code about ga shape inside flags

* update

* update

* add x101 config files

* add ga_rpn r101 config

* update some comments

* add comments

* add comments

* update comments

* fix flake8 error

* Reformat use yapf 0.27.0

* Add yapf style file

* add fcos

* use P5 instead of C5

* add relu before extra convs in FPN

* add singleclass_nms, use caffe2 lr

* fix log interval

* use caffe2init and relu in extra layers

* fix scale layer, use p5 instead of c5

* fix focs target

* refactor code

* delete useless file

* clean

* refactor code

* change num_classes to cls_out_channels

* fix bug of in get_bboxes

* fix bug in test

* add r101 2x cfg

* ms use value mode, add x101-64x4d cfg

* add more comment and rename some variable

* rename centers to points, modify doc string of distance2bbox

* add fcos detector, replace frozen with requires_grad

* add README.md

* add r101-1x performance, rename cfg, add detector FCOS

* update fcos r50 2x performance, remove fpn caffe2 initialize

* fix flake8 error

* rename cfg

* fix grammar error of some comments

* minor fix comment

* change work_dir to be consistent with config name

* add FCOS support in README

* fix OHEM with cascade_rcnn

* fix OHEM with cascade_rcnn

* delete space

* delete white space

* delete unused lib

* Delete cascade_rcnn_ohem_r101_fpn_1x.py

* fix unreasonable code

* fix Single quote

* fix code style

* fix code style

* fix file permission