fix bug: PAFPN has no attribute extra_convs_on_inputs

[luuuyi]

PAFPN has no attribute extra_convs_on_inputs

retinanet-like detectors can use PAFPN

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #4235 (8fc55fe) into master (3e902c3) will decrease coverage by 0.01%.
The diff coverage is 16.66%.

@@            Coverage Diff             @@
##           master    #4235      +/-   ##
==========================================
- Coverage   62.66%   62.65%   -0.02%     
==========================================
  Files         232      232              
  Lines       17597    17601       +4     
  Branches     2942     2944       +2     
==========================================
  Hits        11028    11028              
- Misses       6031     6035       +4     
  Partials      538      538              

Flag	Coverage Δ
unittests	62.61% <16.66%> (-0.02%)	⬇️

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

Impacted Files	Coverage Δ
mmdet/models/necks/pafpn.py	39.58% <0.00%> (-3.60%)	⬇️
mmdet/models/losses/cross_entropy_loss.py	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 3e902c3...29d120f. Read the comment docs.

[hellock]

Could you fix the linting error?

[luuuyi]

Could you fix the linting error?

sorry, the first lint error is some code line is too long. Ifix it, but the second lint error is yapf: files were modified by this hook. I have no idea how to fix it. Could you help me?

[hellock]

It can be merged since the linting error has been fixed. You can just ignore the errors appearing in build_parrots.