title: Matplotlib barchart legend only shows one item
body: <p>When creating a legend for a barchart plot, only the first element of the list is added to the legend.</p>
  
  <p>I have tried to print the legend by means of a grouped dataframe, the barchart is an histogram of occurrence </p>
  
  <pre><code>df = pd.DataFrame({'mod': biomarkers})
  counts =df.groupby('mod', as_index=False)
  counts.size().plot(kind='bar',width=1.0)
  
  names = np.array(counts.describe())[:,2]
  counts = np.array(counts.describe())[:,3]
  plt.legend(list(names))
  plt.show()
  </code></pre>