covparams: List of vectors, where each vector contains information for one parameter used in the modeling of the time-varying covariates (e.g., model statement, family, link function, etc.).
covlink: Vector of link functions.
covfam: Vector of character strings specifying the names of the family functions to be used for fitting the GLM.
obs_data: Data on which the model is fit.
j: Integer specifying the index of the covariate.
model_fits: Logical scalar indicating whether to return the fitted models. The default is FALSE.