title: Convert spark Rdd column to rows in Pyspark
body: <p>I have a spark Rdd which is of form Row(id,Words)
  Where words contains a list of words. I want to convert this list into a single column. 
  Input</p>
  
  <pre><code>ID  Words
  1   [w1,w2,w3]
  2   [w3,w4]
  </code></pre>
  
  <p>I want to convert this to the output format</p>
  
  <pre><code>ID  Word
  1   w1
  1   w2
  1   w3
  2   w3
  2   w4
  </code></pre>