MixedLMResults.
covjhj
covariance of parameters based on HJJH
dot product of Hessian, Jacobian, Jacobian, Hessian of likelihood
name should be covhjh
statsmodels.regression.mixed_linear_model.MixedLMResults.covjac
statsmodels.regression.mixed_linear_model.MixedLMResults.df_modelwc