title: matplotlib empty legend handles
body: <p>I wanted to add some text to a legend in a matplotib plot in python. I was thinking about creating an empty handle, is there any way to do it? Already tried by using somethin similar to:</p>
  
  <pre><code>ax.legend([handle1,handle2,None],[label1,label2,labelEmpty])
  </code></pre>
  
  <p>but legend does not accept the None keyword. ( I get the error $Legend does not support None, Use proxy artist instead.$)</p>
  
  <p>If this is not possible any other ideas?</p>
  
  <p>I am thinking on having something like:</p>
  
  <pre><code> ___________________________
  |  handle1  -  label1       |
  |  handle2  -  label2       |
  |       labelEmpty          |
  !___________________________!
  </code></pre>
  
  <p>thanks!</p>