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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 mahalanobis(self):
 """" Mahalanobis distance of measurement. E.g. 3 means measurement was 3 standard deviations away from the predicted value. Returns ------- mahalanobis : float """

        if self._mahalanobis is None:
            self._mahalanobis = sqrt(float(dot(dot(self.y.T, self.SI), self.y)))
        return self._mahalanobis