chore: deprecate expansion functional utilities method.

[stevenhua0320]

@sbillinge ready to review. Note that originally we don't have tests for these method, so I added them in file test_expansion.py

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.16%. Comparing base (810ef8a) to head (5f64982).
⚠️ Report is 5 commits behind head on v3.4.0.

Additional details and impacted files

@@            Coverage Diff             @@
##           v3.4.0     #178      +/-   ##
==========================================
+ Coverage   99.15%   99.16%   +0.01%     
==========================================
  Files          14       15       +1     
  Lines        2359     2400      +41     
==========================================
+ Hits         2339     2380      +41     
  Misses         20       20              

Files with missing lines	Coverage Δ
tests/test_expansion.py	100.00% <100.00%> (ø)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[sbillinge]

super! Thanks!