title: Pandas merge two columns into Json
body: <p>I have a pandas dataframe like below</p>
  
  <pre><code>    Col1    Col2
  0     a     apple
  1     a     anar
  2     b     ball
  3     b     banana
  </code></pre>
  
  <p>I am looking to output json which outputs like</p>
  
  <pre><code>{ 'a' : ['apple', 'anar'], 'b' : ['ball', 'banana'] }
  </code></pre>