title: Map Iterable Tuple2 to Tuple2
body: <p>I have a <code>JavaPairRDD&lt;String, Iterable&lt;Tuple2&lt;String, Double&gt;&gt;&gt;</code>
  I want to get a <code>JavaPairRDD&lt;Tuple2&lt;Tuple2&lt;String, String&gt;Double&gt;</code> because I want to reduce it by key afterwards. </p>
  
  <pre><code>JavaPairRDD&lt;Tuple2&lt;String, String&gt;,Double&gt; reduceBK = x.reduceByKey(new Function2&lt;Double,Double,Double&gt;() {
              public Double call(Double a,Double b) { return a+b;}
              });
  </code></pre>
  
  <p>How can I transform the Tuple2 with the list inside?</p>