title: Make part of a matplotlib title bold and a different color
body: <p>I would like to change part of a title to be bold. For example:</p>
  
  <pre><code>plt.title("This is title number: " + str(number))
  </code></pre>
  
  <p>Given a title like the above, how would I bold the <code>str(number)</code> part.</p>