title: Find the max value in a dictionary
body: <p>I need to find the maximal value in a nested dictionary, </p>
  
  <pre><code>data = {'violations': {'fatal': {'col1': 1, 'col2': 7, 'col3': 9}}}
  </code></pre>
  
  <p>so how to find the max value in keys <code>col1</code>,<code>col2</code> and <code>col3</code> in <code>data.violations.fatal</code>.</p>