title: How can I draw labels and legend of nested pie charts using python？
body: <p>my code is like this:</p>
  <pre><code>import matplotlib.pyplot as plt
  import numpy as np
  fig, ax = plt.subplots()
  
  size = 0.3
  vals = np.array([[60., 32.], [37., 40.], [29., 10.]])
  
  cmap = plt.colormaps[&quot;tab20c&quot;]
  outer_colors = cmap(np.arange(3)*4)
  inner_colors = cmap([1, 2, 5, 6, 9, 10])
  
  ax.pie(vals.sum(axis=1), radius=1, colors=outer_colors,
         wedgeprops=dict(width=size, edgecolor='w'))
  
  ax.pie(vals.flatten(), radius=1-size, colors=inner_colors,
         wedgeprops=dict(width=size, edgecolor='w'))
  
  ax.set(aspect=&quot;equal&quot;, title='Pie plot with `ax.pie`')
  plt.show()
  </code></pre>
  <p>Please kindly tell me how to add labels to a nested pie charts？</p>