* add isort config

* use isort to sort imports

* add isort to travis

* Added Registry use for validation datasets (distributed)

* Allowing for default_args for build_dataset

* Using build_dataset instead of build_from_cfg

* add fp16 support

* fpn donot need bn normalize

* refactor wrapped bn

* fix bug of retinanet

* add fp16 ssd300 voc, cascade r50, cascade mask r50

* fix bug in cascade rcnn testing

* add support to fix bn training

* add fix bn cfg

* delete fixbn cfg, mv fixbn fp16 to a new branch

* fix cascade mask fp16 bug in test

* fix bug in cascade mask rcnn fp16 test

* add more fp16 cfgs

* add fp16 fast-r50 and faster-dconv-r50

* add fp16 test, minor fix

* clean code

* fix config work_dir name

* add patch func, refactor code

* fix format

* clean code

* move convert rois to single_level_extractor

* fix bug for cascade mask, the seg mask is ndarray

* refactor code, add two decorator force_fp32 and auto_fp16

* add fp16_enable attribute

* add more comment, fix format and test assertion

* fix pep8 format error

* format commont and api

* rename distribute to distributed, fix dict copy

* rename function name

* move function, add comment

* remove unused parameter

* mv decorators into decorators.py, hook related functions to hook

* add auto_fp16 to forward of semantic head

* add auto_fp16 to all heads and fpn

* add docstrings and minor bug fix

* simple refactoring

* bug fix for patching forward method

* roi extractor in fp32 mode

* fix flake8 error

* fix ci error

* add fp16 support to ga head

* remove parallel test assert

* minor fix

* add comment in build_optimizer

* fix typo in comment

* fix typo enable --> enabling

* udpate README

* 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

* support param-wise optimizer settings

* fix outdated docstring

* minor fix for param checking