title: Convert groupby values into list of arrays
body: <p>Here's a sample dataframe:</p>
  
  <pre><code>label  data
  a      1.09
  b      2.1
  a      5.0
  b      2.0
  c      1.9
  </code></pre>
  
  <p>What I want is</p>
  
  <pre><code>arr = [[1.09, 5.0], [2.1, 2.0],[1.9]]
  </code></pre>
  
  <p>preferably as a list of numpy arrays.</p>
  
  <p>I know that <code>df.groupby.groups.keys()</code> gives me the list <code>['a','b','c']</code>, and <code>df.groupby.groups.values()</code> gives me something like <code>arr</code>, but as an <code>Int64Index</code> object. However, I tried <code>df.loc[df.groupby.groups.values()]['label']</code> and it isn't getting the desired result.</p>
  
  <p>How do I accomplish this? Thanks!</p>