title: Pandas pivot table with column as dictionary
body: <p>I have a dataframe which looks like this. Only <code>order</code> is unique.</p>
  
  <pre><code>vendor  order order_class    time
  33       33     42        22/12/2018
  33       39     189       25/12/2018
  35       197    91        19/01/2019
  35       22     189       18/12/2018
  35       11     189       30/11/2018
  </code></pre>
  
  <p>How do I pivot my dataframe to look like this, where the keys are <code>order_class</code> and values are <code>[(order1, time1), (order2, time2)]</code></p>
  
  <pre><code>vendor   dict
  33       {42 : [(33, 25/12/2018)], 189 : [(39, 25/12/2018)]}
  35       {91 : [(197, 19/01/2019)], 189: [(22, 18/12/2018), (11, 30/11/2018)]}
  </code></pre>
  
  <p>*EDITED </p>
  
  <p>An order class can have multiple (order, time) values which needs to be stored in a list.</p>