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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def valid(self,individuals=None,F=None):
 """returns the sublist of individuals with valid fitness."""

        if F:
            valid_locs = self.valid_loc(F)
        else:
            valid_locs = self.valid_loc(self.F)

        if individuals:
            return [ind for i,ind in enumerate(individuals) if i in valid_locs]
        else:
            return [ind for i,ind in enumerate(self.pop.individuals) if i in valid_locs]