title: how to register graphx Edge class with Kryo?
body: <p>I've been trying to register Edge class with Kryo but I'm always getting the following error.</p>
  <pre><code>java.lang.IllegalArgumentException: Class is not registered: org.apache.spark.graphx.Edge\nNote: To register this class use: kryo.register(org.apache.spark.graphx.Edge.class);
  </code></pre>
  <p>what is wrong with following line?</p>
  <pre><code>sc.getConf.registerKryoClasses(Array(Class.forName(&quot;org.apache.spark.graphx.Edge&quot;)))
  
  </code></pre>
  <p>How should I do it?</p>