Reformat continuous.py

[AlexAndorra]

As discussed in #4049, this PR cleans up continuous.py for better readability of the code:

1. Reorders import statements according to PEP8
2. Blackifies the whole file

In addition, @junpenglao mentioned repeating bits that could be refactored. Do you have specific places in mind Junpeng?
I can make the changes or you can push directly on this PR -- whatever you prefer 🙂

• No breaking changes -- only formatting changes
• No need to mention in RELEASE-NOTES.md

[codecov]

Codecov Report

Merging #4051 into master will increase coverage by 0.00%.
The diff coverage is 92.11%.

@@           Coverage Diff           @@
##           master    #4051   +/-   ##
=======================================
  Coverage   88.47%   88.48%           
=======================================
  Files          88       88           
  Lines       13860    13865    +5     
=======================================
+ Hits        12263    12268    +5     
  Misses       1597     1597           

Impacted Files	Coverage Δ
pymc3/distributions/continuous.py	92.82% <92.11%> (+0.04%)	⬆️

[junpenglao]

Some of the Black formatting I am not sure it is making the code better or worse 😂

[AlexAndorra]

Ha ha yeah, I see what you mean! I think this is always a trade-off though, as it also makes some parts of the code much clearer -- so I hope on balance it's better 😅
I just added a pyproject.toml file at the root, to set the vertical limit at 100 instead of 88 -- as we do on ArviZ. Should help with the trade-off 😉

Thanks a lot for all these reformatting proposals, I'll look at that ASAP!

[AlexAndorra]

Turns out the "ASAP" was a bit long this time around, but I added your suggested reformattings @junpenglao 😉
Tell me what you think, and let's see if tests pass!

[AlexAndorra]

Fixing merge conflicts then self-merging if nobody has strong feelings against this reformatting -- to avoid further merge conflicts

[canyon289]

Black is making some of the lines worse to read as @junpenglao mentioned, but knowing how black doesn't care about our feelings Im not sure what you can do about it