# Codeblock 3c
    def forward(self, x):
        print(f'original\t\t: {x.size()}')
        
        if self.add_channel or self.downsample:              #(1)
            residual = self.bn_proj(self.projection(x))      #(2)
            print(f'after projection\t: {residual.size()}')
        else:
            residual = x                                     #(3)
            print(f'no projection\t\t: {residual.size()}')
        
        x = self.conv0(x)    #(4)
        x = self.bn0(x)
        x = self.relu(x)
        print(f'after conv0-bn0-relu\t: {x.size()}')

        x = self.conv1(x)
        x = self.bn1(x)
        x = self.relu(x)
        print(f'after conv1-bn1-relu\t: {x.size()}')
        
        x = self.conv2(x)    #(5)
        x = self.bn2(x)
        print(f'after conv2-bn2\t\t: {x.size()}')
        
        x = x + residual
        x = self.relu(x)     #(6)
        print(f'after summation\t\t: {x.size()}')
        
        return x