Covariance in scalar
l1 (int) – l1 in \(E[y_n^{l_1}y_{n+1}^{l_2}]\).
l2 (int) – l2 in \(E[y_n^{l_1}y_{n+1}^{l_2}]\).
par (dict) – parameters in dict.
scalar of the covariance.
float