Mem time redo

[cdc-mitzimorris]

This PR adds more tests for pyrenew_hew's PyrenewHEWData class.

This is part 1 of a do-over of #709. It doesn't change any of the code in pyrenew_hew_data.py, except to add a docstring for function to_forecast_data. PR 709 made a breaking change to this function; the added documentation is intended prevent future mistakes.

Part 2 of this do-over will use the functions in PyRenew/pyrenew/time.py. specifically:

• align_observation_times
• create_date_time_spine
• get_end_date
• get_n_data_days
• validate_mmwr_dates,

Currently, these are defined as methods in class PyrewnewHEWData; part 2 will change the calls in PyrewnewHEWData from self.get_end_date to get_end_date, etc.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 26.28%. Comparing base (73f78d4) to head (78dcf8e).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #733      +/-   ##
==========================================
+ Coverage   26.08%   26.28%   +0.20%     
==========================================
  Files          26       26              
  Lines        2427     2427              
==========================================
+ Hits          633      638       +5     
+ Misses       1794     1789       -5     

Flag	Coverage Δ
hewr	29.93% <ø> (ø)
pipelines	3.05% <ø> (ø)
pyrenew_hew	64.07% <100.00%> (+0.88%)	⬆️

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[damonbayer]

LGTM, with a few small suggestions.