Calculates the score vector for the profiled log-likelihood of the mixed effects model with respect to the parameterization in which the random effects covariance matrix is represented in its full form (not using the Cholesky factor).
params : MixedLMParams or array-like
The score vector, calculated at `params`. :
The score vector that is returned is taken with respect to the parameterization in which cov_re is represented through its lower triangle (without taking the Cholesky square root).
The input, if provided as a MixedLMParams object, can be of any parameterization.