class my_net(nn.Module):
    def __init__(self):
        super(my_net, self).__init__()
        self.features1 = torch.nn.Sequential(
                            torch.nn.Conv2d(3, 5, 3, padding=1),
                            torch.nn.ReLU(),
                            torch.nn.Conv2d(5, 10, 3, padding=1),
                            )
                            # Take the output of this layer as the input of net2
         self.features2 = torch.nn.Sequential(
                            torch.nn.ReLU(),
                            torch.nn.Conv2d(10, 15, 3, padding=1)
                            )
    def forward(self, x):
        x1 = self.features1(x)
        x2 = self.features2(x1)
        return (x1,x2)

Should be enough in my opinion