Use pep8-compliant pyparsing references

[Andy-Grigg]

Closes #876

Replace all deprecated pyparsing CamelCase references with snake_case variants.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.72%. Comparing base (5d9c830) to head (5d503f4).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #875      +/-   ##
==========================================
- Coverage   94.73%   94.72%   -0.01%     
==========================================
  Files           7        7              
  Lines         797      796       -1     
==========================================
- Hits          755      754       -1     
  Misses         42       42              

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