set implicit optional to true in mypy config to avert side effects and test fails from new mypy version

[valeriupredoi]

Description

Suggested by @zklaus in #1787 (review) which this PR supersedes #1787

Closes #1788

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[valeriupredoi]

OK it looks like that did the trick partially: from 9 to 1 failed mypy test, can I get some help from the standards experts @zklaus @bouweandela @schlunma please - am no good at these things, and wouldn't know what to fix now 🍺

[schlunma]

You could either try using the option --check-untyped-defs as suggested or remove the type hints here:

ESMValCore/esmvalcore/_task.py

Line 739 in b880462

running: Dict[Type[BaseTask], Type[ApplyResult]] = {}

and add them to a comment maybe?

[valeriupredoi]

well that escalated real quick - I'll see about removing the Type from _task.py 🤦‍♂️

[codecov]

Codecov Report

Merging #1790 (5442a76) into main (b880462) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1790      +/-   ##
==========================================
- Coverage   91.11%   91.11%   -0.01%     
==========================================
  Files         203      203              
  Lines       10908    10906       -2     
==========================================
- Hits         9939     9937       -2     
  Misses        969      969              

Impacted Files	Coverage Δ
esmvalcore/_task.py	72.23% <100.00%> (-0.13%)	⬇️

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[valeriupredoi]

OK so I eventually got this through the mypy hoops but am not sure of the functionality I hacked out - @bouweandela could you have a look please? 🍺

[schlunma]

Thanks V.! 🚀

Sorry, this change is exactly what I meant by "remove the type hints", could have been clearer!

[valeriupredoi]

cheers, Manu! Can I nominate @bouweandela to have a looksee at it and merge, please 🍺