How to compute the residual standard deviation from `glmer()` function in R?

#1
I want to extract standard deviation of residual from `glmer()` function in R .

So I wrote :

Code:
    lmer_obj = glmer(Y ~ X1 + X2 + (1|Subj), data = D, family = binomial)
    sigma(lmer_obj)
I noticed that the last command `sigma(lmer_obj)` returns always "1" irrespective of data , that is , whether I used `cbpp` data or own simulated data from multilevel logistic distribution , the residual standard error is always 1 .

How can I get the residual standard deviation from `glmer()` function ?