def set_XY(self, X, Y):
        """
        Set the input / output data of the model
        This is useful if we wish to change our existing data but maintain the same model

        :param X: input observations
        :type X: np.ndarray
        :param Y: output observations
        :type Y: np.ndarray or ObsAr
        """
        self.update_model(False)
        self.set_Y(Y)
        self.set_X(X)
        self.update_model(True)