The function `G_estimate` uses a MoM method, and `G_estimate_randint` is a special case of `G_estimate`.
G_generate(data, Z_lst, RE_table, MoM, ID = "id")
List containing Z matrices and indices (unsure)
Data frame that contains the predictors and outcome
Transposed list of Z matrices from the univariate fits
Table of random effects and interactions, generated from the `lmerMod` object
Integer to determine type of MoM estimation.
Name of the ID factor, assuming names of `HHat` are generated from the same table in the same order
Helper function for variance estimation in `fui`.