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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 fitness(self, parsimony_coefficient=None):
 """Evaluate the penalized fitness of the program according to X, y. Parameters parsimony_coefficient : float, optional If automatic parsimony is being used, the computed value according to the population. Otherwise the initialized value is used. Returns ------- fitness : float The penalized fitness of the program. """

        if parsimony_coefficient is None:
            parsimony_coefficient = self.parsimony_coefficient
        penalty = parsimony_coefficient * len(self.program) * self.metric.sign
        return self.raw_fitness_ - penalty