title: Use dataframe column names as labels in pylab.plot
body: <p>I would like to plot the data in a dataframe and have the column headers be the labels.  I tried this:</p>
  
  <pre><code>dfm.columns = ['a','b']
  plot(dfm.cumsum(), label= dfm.columns.values)
  legend(loc='upper left')
  </code></pre>
  
  <p>But got this:</p>
  
  <p><a href="https://i.stack.imgur.com/khAc2.png" rel="noreferrer"><img src="https://i.stack.imgur.com/khAc2.png" alt="enter image description here"></a></p>
  
  <p>Instead of both lines being labeled ['a','b'], I'd like the blue line to be a and the green to be b using <code>pylab</code></p>