title: What is W[...,c] doing?
body: <p>What is this selection using "..." doing in this context?</p>
  
  <p><code>Z[i, h, w, c] = conv_single_step(a_slice_prev, W[...,c], b[...,c])</code></p>
  
  <p>Is it a similar operation to X[:,:] but with some other context that I am unable to find?</p>