title: Bokeh heatmap from Pandas confusion matrix
body: <p>How can a Pandas <code>DataFrame</code> be shown as a Bokeh heatmap?</p>
  
  <p><a href="https://docs.bokeh.org/en/latest/docs/user_guide/categorical.html#heat-maps" rel="nofollow noreferrer">https://docs.bokeh.org/en/latest/docs/user_guide/categorical.html#heat-maps</a> shows some example, but trying to modify always only gave an empty plot.</p>
  
  <p>Example confusion matrix:</p>
  
  <pre><code>df = pd.DataFrame([[10, 0, 1], [1, 10, 0], [1, 1, 9]], 
                    columns=['A', 'B', 'C'], 
                    index=['A', 'B', 'C'])
  df.index.name = 'Treatment'
  df.columns.name = 'Prediction'
  </code></pre>