Computes the weights for the scaled unscented Kalman filter.

def _compute_weights(self):
        """ Computes the weights for the scaled unscented Kalman filter.

        """

        n = self.n
        lambda_ = self.alpha**2 * (n +self.kappa) - n

        c = .5 / (n + lambda_)
        self.Wc = np.full(2*n + 1, c)
        self.Wm = np.full(2*n + 1, c)
        self.Wc[0] = lambda_ / (n + lambda_) + (1 - self.alpha**2 + self.beta)
        self.Wm[0] = lambda_ / (n + lambda_)