title: Combined legend entry for plot and fill_between
body: <p>This is similar to <a href="https://stackoverflow.com/questions/17617190/matlab-combine-the-legends-of-shaded-error-and-solid-line-mean">Matlab: Combine the legends of shaded error and solid line mean</a>, except for Matplotlib. Example code:</p>
  
  <pre><code>import numpy as np
  import matplotlib.pyplot as plt
  
  x = np.array([0,1])
  y = x + 1
  f,a = plt.subplots()
  a.fill_between(x,y+0.5,y-0.5,alpha=0.5,color='b')
  a.plot(x,y,color='b',label='Stuff',linewidth=3)
  a.legend()
  
  plt.show()
  </code></pre>
  
  <p>The above code produces a legend that looks like this:</p>
  
  <p><img src="https://i.stack.imgur.com/ThYE0.png" alt="enter image description here"></p>
  
  <p>How can I create a legend entry that combines the shading from <code>fill_between</code> and the line from <code>plot</code>, so that it looks something like this (mockup made in Gimp):</p>
  
  <p><img src="https://i.stack.imgur.com/wkOsd.png" alt="enter image description here"></p>