Add some type annotations

[peterallenwebb]

Description

Add some type annotations

Checklist

• I have read the contributing guide and understand what's expected of me
• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 64.33%. Comparing base (db99ddd) to head (59c8a9e).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #156      +/-   ##
==========================================
+ Coverage   64.31%   64.33%   +0.02%     
==========================================
  Files          51       51              
  Lines        3228     3230       +2     
==========================================
+ Hits         2076     2078       +2     
  Misses       1152     1152              

Flag	Coverage Δ
unit	64.33% <100.00%> (+0.02%)	⬆️

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[QMalcolm]

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