diff --git a/docs/compatibility.md b/docs/compatibility.md
index 2eeae99e847..477a83d83f9 100644
--- a/docs/compatibility.md
+++ b/docs/compatibility.md
@@ -2,10 +2,10 @@
 
 ## Mask AP Evaluation since MMDetection 2.12.0
 
-Before [PR 4898](https://github.com/open-mmlab/mmdetection/pull/4898) and V2.13.0, the mask AP of small, medium, and large instances is calculated based on the bounding box area rather than the real mask area. This leads to higher APs and APm but lower APl but will not affect the overall mask AP. 
+Before [PR 4898](https://github.com/open-mmlab/mmdetection/pull/4898) and V2.12.0, the mask AP of small, medium, and large instances is calculated based on the bounding box area rather than the real mask area. This leads to higher APs and APm but lower APl but will not affect the overall mask AP.
 [PR 4898](https://github.com/open-mmlab/mmdetection/pull/4898) change it to use mask areas by deleting `bbox` in mask AP calculation.
 The new calculation is consistent with [Detectron2](https://github.com/facebookresearch/detectron2/).
- 
+
 ## Compatibility with MMDetection 1.x
 
 MMDetection 2.0 goes through a big refactoring and addresses many legacy issues. It is not compatible with the 1.x version, i.e., running inference with the same model weights in these two versions will produce different results. Thus, MMDetection 2.0 re-benchmarks all the models and provides their links and logs in the model zoo.
diff --git a/mmdet/datasets/coco.py b/mmdet/datasets/coco.py
index 1a6ec3d3f03..2a6c2dbda75 100644
--- a/mmdet/datasets/coco.py
+++ b/mmdet/datasets/coco.py
@@ -1,8 +1,8 @@
 import itertools
-import warnings
 import logging
 import os.path as osp
 import tempfile
+import warnings
 from collections import OrderedDict
 
 import mmcv