Rename PTF_formula to ptf_formula with a deprecation alias

[Abhayindia]

Summary of Changes

Renames PTF_formula to ptf_formula. The old name stays as a thin wrapper that emits a DeprecationWarning and forwards to the new one, so nothing breaks for 0.11.0. The internal caller in barnzehn.py is switched to the new name.

Related GitHub Issue(s)

Closes #1291

Additional Context for Reviewers

Added test_ptf_formula_deprecated_alias — checks the alias warns and returns the same formula string. ruff check --config lint.per-file-ignores={} and ruff format --check pass on the three changed files; pytest chainladder/development/tests/test_barnzehn.py passes. Couldn't run the doctest builder locally (no jb), but no docs reference PTF_formula.

Checklist

• I passed tests locally for code changes (documentation unaffected)

[github-actions]

Pyright Type Completeness

View the full pyright --verifytypes output for this commit

Project (full chainladder package, at this PR's head): 15.0% of exported symbols fully typed (208 / 1384)

	Known	Ambiguous	Unknown	Total
Project (head)	208	111	1065	1384

Other symbols referenced but not exported by chainladder: 13

	Known	Ambiguous	Unknown	Total
Other (head)	3	1	9	13

Symbols without documentation:

• Functions without docstring: 327
• Functions without default param: 0
• Classes without docstring: 10

Patch (exported symbols added or changed by this PR): 50.0% fully typed (1 / 2)

	Known	Ambiguous	Unknown	Total
Patch	1	0	1	2

Patch symbol details

Symbol	Status	Change
chainladder.utils.tests.test_utilities.test_ptf_formula_deprecated_alias	✅ known	new
chainladder.utils.utility_functions.ptf_formula	❌ unknown	new

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.73%. Comparing base (d82c521) to head (c19902a).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1316      +/-   ##
==========================================
+ Coverage   91.79%   92.73%   +0.94%     
==========================================
  Files          96       98       +2     
  Lines        5494     6206     +712     
  Branches      707      839     +132     
==========================================
+ Hits         5043     5755     +712     
- Misses        327      329       +2     
+ Partials      124      122       -2     

Flag	Coverage Δ
unittests	92.70% <100.00%> (+0.90%)	⬆️

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[genedan]

Note to reviewers: I'd like for #1318 to be resolved before we review/close this.

[genedan]

FYI the PR with the new deprecation tools is this one #1323. It's still under review but it should give you a general idea on the new tools that will be available to you to complete this PR.

[Abhayindia]

thanks, that's helpful - _deprecated_rename in #1323 is exactly what this PR is hand-rolling right now (a PTF_formula wrapper that calls warnings.warn then delegates to ptf_formula), so it should collapse to a decorator once that lands.
happy to swap it over, but i'll hold until #1323 is merged rather than build against an API that's still in review - ping me when it's in and i'll rebase this onto it.

[henrydingliu]

@Abhayindia github overreacting...

@genedan i don't think you meant to close it. please confirm

[genedan]

Must have been an accident.

@Abhayindia, the new deprecation tools are ready. FYI, we changed which function will be the wrapper. The old_func should be the wrapper around new_func.

[genedan]

It's because I said "needed to close #XXXX" in another PR. Guess I gotta change my language..."blocker for #XXXX"?