title: make a spark rdd from tuples list and use groupByKey
body: <p>I have a list of tuples like below </p>
  
  <pre><code>ls=[('c', 's'),('c', 'm'), ('c', 'p'), ('h', 'bi'), ('h', 'vi'), ('n', 'l'), ('n', 'nc')]
  </code></pre>
  
  <p>I would like to use pyspark and groupByKey to produce: </p>
  
  <pre><code>nc=[['c','s', 'm', 'p'], ['h','bi','vi'], ['n','l', 'nc']
  </code></pre>
  
  <p>I dont know how to make a spark rdd and use groupByKey. </p>
  
  <p>I tried: </p>
  
  <pre><code>tem=ls.groupByKey()  
  </code></pre>
  
  <blockquote>
    <p><code>'list' object has no attribute 'groupByKey'</code></p>
  </blockquote>