Prevent mutation of supp_pub.protected in to_cis.

[dajiaji]

Closes #521

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.34%. Comparing base (0f363df) to head (35ac7c7).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #630   +/-   ##
=======================================
  Coverage   97.34%   97.34%           
=======================================
  Files          32       32           
  Lines        3351     3352    +1     
=======================================
+ Hits         3262     3263    +1     
  Misses         89       89           

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