auto-gen a GeneratedBy dict

[drammock]

PR Description

closes #1383

Merge checklist

Maintainer, please confirm the following before merging.
If applicable:

• All comments are resolved
• This is not your own PR
• All CIs are happy
• PR title starts with [MRG]
• whats_new.rst is updated
• New contributors have been added to CITATION.cff
• PR description includes phrase "closes <#issue-number>"

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.47%. Comparing base (a36db9e) to head (1d740b7).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1384   +/-   ##
=======================================
  Coverage   97.47%   97.47%           
=======================================
  Files          40       40           
  Lines        9024     9025    +1     
=======================================
+ Hits         8796     8797    +1     
  Misses        228      228           

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[sappelhoff]

Thanks!