title: How to understand Seaborn's heatmap annotation format
body: <p>I am looking for a way to show "0.0045" as "0.45%" on <code>seaboarn</code>'s heatmap by specifying the <code>fmt</code> keyword:</p>
  
  <pre><code>sns.heatmap(data, annot=True, fmt='??')
  </code></pre>
  
  <p>However, I did not find a list of format to use. Searching between different examples, I have seen "d", ".2g", ".1f", ".1f%". But it is not clear what is the convention we are assuming here.</p>
  
  <p>Is this assuming people have a common understanding of the formatting format? Or this is present on a doc page I missed?</p>