title: NumPy calculate square of norm 2 of vector
body: <p>I have vector <code>a</code>.<br>
  I want to calculate <code>np.inner(a, a)</code><br>
  But I wonder whether there is prettier way to calc it.</p>
  
  <p>[The disadvantage of this way, that if I want to calculate it for <code>a-b</code> or a bit more complex expression, I have to do that with one more line. <code>c = a - b</code> and <code>np.inner(c, c)</code> instead of <code>somewhat(a - b)</code>]</p>