title: Add extra hours to timestamp columns in Pyspark data frame
body: <p>I have a data frame in <code>Pyspark</code>. In this data frame I have a column which is of <code>timestamp</code> data type. Now I want to add extra 2 hours for each row of the timestamp column without creating any new columns. </p>
  
  <p>For Example: This is sample data</p>
  
  <p><code>df</code></p>
  
  <pre><code>id  testing_time            test_name
  
  1   2017-03-12 03:19:58     Raising
  2   2017-03-12 03:21:30     sleeping
  3   2017-03-12 03:29:40     walking
  4   2017-03-12 03:31:23     talking
  5   2017-03-12 04:19:47     eating  
  6   2017-03-12 04:33:51     working
  </code></pre>
  
  <p>I want to have something like below.</p>
  
  <p><code>df1</code>   </p>
  
  <pre><code>id  testing_time            test_name
  
  1   2017-03-12 05:19:58     Raising
  2   2017-03-12 05:21:30     sleeping
  3   2017-03-12 05:29:40     walking
  4   2017-03-12 05:31:23     talking
  5   2017-03-12 06:19:47     eating  
  6   2017-03-12 06:33:51     working 
  </code></pre>
  
  <p>How can I do that?</p>