mypy: Use "|" operator instead of Union/Optional

[rht]

Partially addresses #1341. To completely remove Union, sadly, we need to wait until 3.10 is the oldest supported version.

See https://peps.python.org/pep-0604/.

[codecov]

Codecov Report

Merging #1345 (03419e1) into main (991a017) will increase coverage by 0.16%.
The diff coverage is 100.00%.

❗ Current head 03419e1 differs from pull request most recent head 38d662e. Consider uploading reports for the commit 38d662e to get more accurate results

@@            Coverage Diff             @@
##             main    #1345      +/-   ##
==========================================
+ Coverage   90.97%   91.13%   +0.16%     
==========================================
  Files          19       19              
  Lines        1329     1342      +13     
  Branches      256      257       +1     
==========================================
+ Hits         1209     1223      +14     
+ Misses         85       84       -1     
  Partials       35       35              

Impacted Files	Coverage Δ
mesa/agent.py	77.77% <100.00%> (+1.30%)	⬆️
mesa/model.py	100.00% <100.00%> (ø)
mesa/space.py	94.72% <100.00%> (+0.27%)	⬆️
mesa/time.py	94.79% <100.00%> (+0.05%)	⬆️
mesa/visualization/UserParam.py	95.00% <0.00%> (+0.38%)	⬆️

---

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 991a017...38d662e. Read the comment docs.

[rht]

@wang-boyu CI failed here. How did you make it work?

[wang-boyu]

I'm guessing it's due to the type aliases TimeT = float | int, GridContent = Agent | None etc.

From here it mentions

Even with the future import, there are some scenarios that could still require string literals or result in errors, typically involving use of forward references or generics in:
type aliases;
...

A similar issue was reported: python/mypy#9610

[Corvince]

TimeT: TypeAlias = float | int potentially fixes this, from what I read

[rht]

TimeT: TypeAlias = float | int potentially fixes this, from what I read

I tried this in the 2nd commit. For Python < 3.10, failed with the following error message:

E   ImportError: cannot import name 'TypeAlias' from 'typing' 

[rht]

TimeT: TypeAlias = float | int potentially fixes this, from what I read

I tried this in the 2nd commit. For Python < 3.10, failed with the following error message:

E   ImportError: cannot import name 'TypeAlias' from 'typing' 

[rht]

I think I will use Union for the type aliases for now. Only 4 lines of code need them. The rest can be safely set to use |.

[rht]

PR is ready for review.

[tpike3]

LGTM