I am trying to understand some code in which I found this statement. I don't know what "@" sign is doing here.
This is a running code for landmark detection, you can check full code here: https://github.com/cleardusk/3DDFA/blob/master/utils/ddfa.py
vertex = p @ (u + w_shp @ alpha_shp + w_exp @ alpha_exp).reshape(3, -1, order='F') + offset