title: getting the opposite diagonal of a numpy array
body: <p>So in numpy arrays there is the built in function for getting the diagonal indices, but I can't seem to figure out how to get the diagonal starting from the top right rather than top left. </p>
  
  <p>This is the normal code to get starting from the top left:</p>
  
  <pre><code>&gt;&gt;&gt; import numpy as np
  &gt;&gt;&gt; array = np.arange(25).reshape(5,5)
  &gt;&gt;&gt; diagonal = np.diag_indices(5)
  &gt;&gt;&gt; array
  array([[ 0,  1,  2,  3,  4],
     [ 5,  6,  7,  8,  9],
     [10, 11, 12, 13, 14],
     [15, 16, 17, 18, 19],
     [20, 21, 22, 23, 24]])
  &gt;&gt;&gt; array[diagonal]
  array([ 0,  6, 12, 18, 24])
  </code></pre>
  
  <p>so what do I use if I want it to return:</p>
  
  <pre><code>array([ 4,  8, 12, 16, 20])
  </code></pre>