title: udf spark column names
body: <p>I need to specify a sequence of columns. If I pass two strings, it works fine</p>
  
  <pre><code>val cols = array("predicted1", "predicted2")
  </code></pre>
  
  <p>but if I pass a sequence or an array, I get an error:</p>
  
  <pre><code> val cols = array(Seq("predicted1", "predicted2"))
  </code></pre>
  
  <p>Could you please help me? Many thanks!</p>