Solved by crcrpar in post #2 
              
              
                Hi, 
self.sgcn2 is sequential of MS_GCN, MS_TCN, and MS_TCN. 
So, self.sgcn2[-1] refers to the last MS_TCN. 
self.sgcn2[-1].act is either the attribute or member variable of an instance of MS_TCN. From that name, I guess by default MS_TCN has some activation function such as Sigmoid and ReLU. Though…