title: Indexing a tensor with None in PyTorch
body: <p>I've seen this syntax to index a tensor in PyTorch, not sure what it means:</p>
  <pre><code>v = torch.div(t, n[:, None])
  </code></pre>
  <p>where <code>v</code>, <code>t</code>, and <code>n</code> are tensors.</p>
  <p>What is the role of &quot;<code>None</code>&quot; here? I can't seem to find it in the documentation.</p>