title: Change Iterable[(String, Double)] of an RDD to Array or List
body: <p>I have an <code>org.apache.spark.rdd.RDD[(String, (Double, Double), Iterable[(String, Double)])]</code> but it seems working with the <code>Iterable</code> is hard. Is there any way I can change it to an <code>Array[(String, Double)]</code>?</p>