Predicts the covariance matric for points in X.

        Parameters:
            X (np.ndarray) - points to run the prediction for.
            with_noise (bool) - whether to add noise to the prediction. Default is True.

def predict_covariance(self, X, with_noise=True):
        """
        Predicts the covariance matric for points in X.

        Parameters:
            X (np.ndarray) - points to run the prediction for.
            with_noise (bool) - whether to add noise to the prediction. Default is True.
        """
        _, v = self._predict(X, True, with_noise)
        return v