object: An object of class "nsga", "nsga2" or "nsga3" usually resulting from a call to function nsga, nsga2, nsga3.
parent: A vector of values for the parent from the current population where mutation should occur.
nm: Parameters of genetic operators.
Returns
Return a vector of values containing the mutated string.
References
Scrucca, L. (2017) On some extensions to 'GA' package: hybrid optimisation, parallelisation and islands evolution. The R Journal, 9/1, 187-206, doi: 10.32614/RJ-2017-008.