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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 fit(self,y_true_cal=None, y_prob_cal=None):
 """ If calibration, then train the calibration of probabilities Parameters y_true_cal : array-like of shape = [n_samples], optional default = None True class to be used for calibrating the probabilities y_prob_cal : array-like of shape = [n_samples, 2], optional default = None Predicted probabilities to be used for calibrating the probabilities Returns ------- self : object Returns self. """

        if self.calibration:
            self.cal = ROCConvexHull()
            self.cal.fit(y_true_cal, y_prob_cal[:, 1])