Question on nlme

Hello,

I am using the nlme package in R:

model <- lme(
    response ~ response_type + x_y + x_z - 1,
    random = ~ response_type - 1 | group,
    weights = varIdent(form = ~ 1 | response_type),
    data = data_long,
    control = lmeControl(opt = "optim")
)

Is it possible to know what estimation process this is using? For example, is it using EM? Or is it use Newton-Raphson with GLS/RMLE?

Thanks!


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