Implementation of YOLACT forward_dummy to enable get_flops

[collinzrj]

Motivation

To enable the get_flops feature on YOLACT, the forward_dummy needs to be implemented

Modification

The forward_dummy function is implemented.

Closes #5891

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #6079 (e0ac5b6) into master (db85fd1) will increase coverage by 0.38%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #6079      +/-   ##
==========================================
+ Coverage   61.44%   61.82%   +0.38%     
==========================================
  Files         304      315      +11     
  Lines       23855    25163    +1308     
  Branches     3942     4185     +243     
==========================================
+ Hits        14657    15558     +901     
- Misses       8415     8796     +381     
- Partials      783      809      +26     

Flag	Coverage Δ
unittests	61.80% <100.00%> (+0.38%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mmdet/models/dense_heads/yolact_head.py	79.55% <100.00%> (+0.17%)	⬆️
mmdet/models/detectors/yolact.py	97.36% <100.00%> (+3.08%)	⬆️
mmdet/models/detectors/yolo.py	50.00% <0.00%> (-33.34%)	⬇️
mmdet/core/bbox/coder/yolo_bbox_coder.py	52.94% <0.00%> (-8.04%)	⬇️
mmdet/models/dense_heads/rpn_head.py	88.00% <0.00%> (-4.86%)	⬇️
mmdet/datasets/api_wrappers/coco_api.py	87.50% <0.00%> (-4.17%)	⬇️
mmdet/models/plugins/dropblock.py	91.89% <0.00%> (-2.40%)	⬇️
mmdet/models/utils/ckpt_convert.py	3.73% <0.00%> (-0.92%)	⬇️
mmdet/models/dense_heads/yolo_head.py	46.66% <0.00%> (-0.92%)	⬇️
mmdet/models/roi_heads/bbox_heads/bbox_head.py	78.87% <0.00%> (-0.75%)	⬇️
... and 35 more

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[collinzrj]

@ZwwWayne

[collinzrj]

The change does not influence test_yolo_normal, is there anything wrong with the CI?

[collinzrj]

@RangiLyu

[collinzrj]

My local lint passed, is there any updates on the docformatter check?

[RangiLyu]

My local lint passed, is there any updates on the docformatter check?

My local lint passed too. Really wired. @hhaAndroid @ZwwWayne any ideas?

[collinzrj]

lint passed @RangiLyu

[collinzrj]

The test failed for something not related to this change

[RangiLyu]

LGTM