title: Calculating gradient with NumPy
body: <p>I really can not understand what <code>numpy.gradient</code> function does and how to use it for computation of <em>multivariable function gradient</em>.</p>
  
  <p>For example, I have such a function:</p>
  
  <pre><code>def func(q, chi, delta):
      return q * chi * delta
  </code></pre>
  
  <p>I need to compute it's 3-dimensional gradient (in other words, I want to compute partial derivatives with respect to all variables (q, chi, delta)).</p>
  
  <p>How can I calculate this gradient using NumPy?</p>