Improve parameter replacement in set_fn function

[ziatdinovmax]

• Use regular expressions with word boundaries to replace parameter names in the source function.
• Ensure robust replacement even in cases where parameter names are surrounded by characters other than spaces, like parentheses.
• This resolves issues with functions that have parameters within expressions or parentheses.

[codecov-commenter]

Codecov Report

Merging #46 (64b1d88) into main (c6dab96) will increase coverage by 0.00%. The diff coverage is 100.00%.

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@@           Coverage Diff           @@
##             main      #46   +/-   ##
=======================================
  Coverage   95.89%   95.89%           
=======================================
  Files          41       41           
  Lines        3407     3408    +1     
=======================================
+ Hits         3267     3268    +1     
  Misses        140      140           

Flag	Coverage Δ
unittests	95.89% <100.00%> (+<0.01%)	:arrow_up:

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Files	Coverage Δ
gpax/utils.py	89.83% <100.00%> (+0.08%)	:arrow_up:

... and 1 file with indirect coverage changes

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