title: How to rotate the data_label values on column chart
body: <p>Trying to rotate the <code>data_label</code> values on the chart to 90 degree since my chart is condensed and the values and overlapping.<br>
  I tried this but its not working, maybe because <code>'num_font':  {'rotation': 90}</code> is only for <code>set_x_axis</code>.</p>
  
  <pre><code>'data_labels': { 'value': True, 'position' : 'outside_end', 'num_font':  {'rotation': 90} }
  </code></pre>