Correspondence of formula and code（torch.cumprod）

[y6216886]

Dear authors:
Thanks for your impressive work. I found the opetation "torch.cumprod" in code
def plane_volume_rendering(rgb_BS3HW, sigma_BS1HW, xyz_BS3HW, is_bg_depth_inf): transparency_acc = torch.cumprod(transparency + 1e-6, dim=1) # BxSx1xHxW
However, I can't see an equation that contains cumprod opetation in paper "MINE:...". Where should I refer to the corresponding formula.
Thanks a lot.