var: a one-sided [formula] object or variable name ([character]) that defines the heteroscedastic variance or [NULL] indicating homoscedastic variance (default: NULL).
na.rm: [logical] indicating whether NA values should be removed before the computation proceeds (default: FALSE).
verbose: [logical] indicating whether additional information is printed to the console (default: TRUE).
...: additional arguments passed to the method (e.g., maxit: maxit number of iterations, etc.).