title: How to convert duration strings to seconds?
body: <p>I have such a column in a pandas dataframe:</p>
  <pre><code>duration
  1 day 22:12:15.778543
  2 days 10:09:07.118723
  00:18:23.985112
  </code></pre>
  <p>I would like to convert this <code>duration</code> to seconds.</p>
  <p>How can I do this? I am not sure if this is possible because of the special string format I got (<code>1 day</code>, <code>2 days</code> etc.)?</p>