title: Use different font properties for label in matplotlib legend
body: <p>I would like to use 2 different font size in the same legend in a matplotlib graph.</p>
  
  <p>For exemple, I would like to use a 15 points bold font for some labels and 10 points normal font for the others labels in the same legend box.</p>
  
  <p>My plot legend already regroup legend from 2 axes (<a href="https://stackoverflow.com/questions/14344063/single-legend-for-multiple-axes">Single legend for multiple axes</a>) and have a variable number of data plotted.</p>
  
  <p>I already use blank data strategy to add annotation to the legend plot (<a href="https://stackoverflow.com/questions/16826711/is-it-possible-to-add-a-string-as-a-legend-item-in-matplotlib">Is it possible to add a string as a legend item in matplotlib</a>). But I would like to make it with a bigger sized, bolt fount if it's possible.</p>
  
  <p>Thank you!</p>