nn.Upsample bilinear mode algorithm

Greetings. I’ve been trying to find more resources about how exactly the output of nn.Upsample is determined when the mode is set to bilinear, but I have yet to find any as I got lost trying to find it in the rabbit hole that is the Pytorch repoistory.

Could anyone refer me to some document or the exact line of code where the bilinear mode for nn.Upsample gets called?