title: Scala convert Iterable or collection.Seq to collection.immutable.Seq
body: <p>It appears the <code>toSeq</code> method in Scala collections returns a <code>scala.collection.Seq</code>, I could also return a <code>Traversable</code> or <code>Iterable</code> but need to convert this to a <code>scala.collection.immutable.Seq</code>.</p>
  
  <p>Is there an easy way to do this?</p>
  
  <p>Thanks
  Richard</p>