title: What do * and mean stand for in this PyTorch expression?
body: <p>I do not understand how to evaluate this expression:</p>
  <pre><code>x.view(*(x.shape[:-2]),-1).mean(-1)`, 
  </code></pre>
  <p>if <code>x.shape == (N, C, H, W)</code>.</p>
  <p>What does the asterisk <code>*</code> stand for? And what is <code>mean(-1)</code> ?</p>