title: How to perform sum pooling in PyTorch
body: <p>How to perform sum pooling in PyTorch. Specifically, if we have input <code>(N, C, W_in, H_in)</code> and want output <code>(N, C, W_out, H_out)</code> using a particular <code>kernel_size</code> and <code>stride</code> just like <code>nn.Maxpool2d</code> ?</p>