title: Framed title spread over the length of X-axis in matplotlib
body: <p>I am trying to replicate a plot produced in R, where each of the subplots in a figure has a framed title over the length of X axis. Like this:</p>
  
  <p><a href="https://i.stack.imgur.com/aAqCo.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/aAqCo.png" alt="enter image description here"></a></p>
  
  <p>I have tried various things with python, but can't really get any further than this (the rest of the arguments are not important at the moment, hence no code):
  <a href="https://i.stack.imgur.com/Dn4fy.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Dn4fy.png" alt="enter image description here"></a></p>
  
  <p>Is there any way of spreading the frame? I found that bbox is treated as a rectangle, and theoretically I should be able to specify the height and width, but when I try to do this like this:</p>
  
  <pre><code>plt.title('A6', bbox = dict(facecolor='grey', edgecolor='black', 
  width=5, height = 5, alpha=0.5))
  </code></pre>
  
  <p>I am getting a TypeError: <strong>init</strong>() got multiple values for argument 'width'</p>