Updates calc_impact code and docstring #2371

Job	Run time
Core / Unit Test Pipeline (3.11)	8m 33s
Core / Unit Test Pipeline (3.10)	17m 56s
Core / Unit Test Pipeline (3.12)	8m 20s
Petals Compatibility / Unit Test Pipeline (3.11)	9m 52s
Petals Compatibility / Unit Test Pipeline (3.10)	20m 25s
Petals Compatibility / Unit Test Pipeline (3.12)	8m 53s
	1h 13m 59s

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