docs(python): Improve over docs, add example with order_by

[MarcoGorelli]

I'm suggesting a few changes to the over docs:

• add an example with order_by
• show how to use mapping_strategy='explode' properly
• simplify a bit

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.85%. Comparing base (6561eba) to head (51b60c5).
Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18796      +/-   ##
==========================================
+ Coverage   79.84%   79.85%   +0.01%     
==========================================
  Files        1518     1518              
  Lines      205576   205563      -13     
  Branches     2892     2892              
==========================================
+ Hits       164132   164151      +19     
+ Misses      40896    40864      -32     
  Partials      548      548              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.