Lesson 7 CAM, why we clip features map > 0

In Lesson7 CAM section,
why is the features map acquired from forward_hook need to be > 0

feat = np.maximum(0,to_np(sfs[3].features[0]))

from CAM paper, Mc(x,y) is class activation map, and w is importance feature of fk


Is it because importance features mean only positive value?