Function hatTrace in package lme4

Dear all, 

For a project I need to calculate the conditional AIC of a mixed effects
model. 
Luckily, I found a reference in the R help forum for a function to be used: 

CAIC <- function(model) { 

        sigma <- attr(VarCorr(model), 'sc') 
        observed <- attr(model, 'y') 
        predicted <- fitted(model) 
        cond.loglik <- sum(dnorm(observed, predicted, sigma, log=TRUE)) 

        rho <- hatTrace(model) 
        p <- length(fixef(model)) 
        N <- nrow(attr(model, 'X')) 
        K.corr <- N*(N-p-1)*(rho+1)/((N-p)*(N-p-2)) +
N*(p+1)/((N-p)*(N-p-2)) 

        CAIC <- -2*cond.loglik + 2*K.corr 

        return(CAIC) 

        } 

Reference:
http://r.789695.n4.nabble.com/Using-Conditional-AIC-with-lmer-td847899.html

However, in this function the function hatTrace of the lme4 package was used
to calcuate rho 
(line:  rho <- hatTrace(model) )

Sadly, R tells me that this function could not be found. A search on the
internet revealed that this function was dropped out of the new package
release of lme4. 

Can anyone help me with this? Is there an alternative function that gives me
the same result as the hatTrace function?