extend typing

[Borda]

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• Did you make sure to update the docs?
• Did you write any new necessary tests?

What does this PR do?

Fixes # (issue).

PR review

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[codecov]

Codecov Report

Merging #324 (90b88c5) into master (4340f35) will increase coverage by 0.08%.
The diff coverage is 97.87%.

@@            Coverage Diff             @@
##           master     #324      +/-   ##
==========================================
+ Coverage   96.50%   96.59%   +0.08%     
==========================================
  Files         111      111              
  Lines        3547     3549       +2     
==========================================
+ Hits         3423     3428       +5     
+ Misses        124      121       -3     

Flag	Coverage Δ
Linux	75.79% <91.48%> (+0.07%)	⬆️
Windows	75.79% <91.48%> (+0.07%)	⬆️
cpu	96.53% <97.87%> (+0.03%)	⬆️
gpu	96.50% <97.87%> (?)
macOS	96.53% <97.87%> (+0.03%)	⬆️
pytest	96.59% <97.87%> (+0.08%)	⬆️
python3.6	95.65% <97.87%> (+0.03%)	⬆️
python3.8	96.53% <97.87%> (+0.03%)	⬆️
python3.9	96.42% <97.87%> (+0.03%)	⬆️
torch1.3.1	95.65% <97.87%> (+0.03%)	⬆️
torch1.4.0	95.74% <97.87%> (+0.03%)	⬆️
torch1.9.0	96.42% <97.87%> (+0.03%)	⬆️

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

Impacted Files	Coverage Δ
torchmetrics/average.py	95.83% <ø> (ø)
...hmetrics/classification/binned_precision_recall.py	100.00% <ø> (ø)
torchmetrics/classification/f_beta.py	100.00% <ø> (ø)
torchmetrics/classification/iou.py	100.00% <ø> (ø)
torchmetrics/classification/kldivergence.py	87.50% <ø> (ø)
torchmetrics/classification/precision_recall.py	100.00% <ø> (ø)
torchmetrics/classification/specificity.py	100.00% <ø> (ø)
torchmetrics/collections.py	98.87% <ø> (ø)
torchmetrics/image/inception.py	95.00% <ø> (ø)
...trics/regression/mean_absolute_percentage_error.py	100.00% <ø> (ø)
... and 37 more

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