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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 get_init_score(self):
 """Get the initial score of the Dataset. Returns ------- init_score : numpy array or None Init score of Booster. """

        if self.init_score is None:
            self.init_score = self.get_field('init_score')
        return self.init_score