betweenness centrality for a multilayer network

[2behappy]

Hi, I was looking for the calculation of the betweenness centrality for a multilayer network in muxViz, but I did not find it.

To be precise, in https://github.com/manlius/muxViz/blob/master/R/muxLib_annotated.R, I found
#betweenness
#todo

Is there any other place where I could find the betweenness centrality calculation for a multilayer network?
If available somewhere else, what are the reference papers for such a metric?

All the best,