title: How do I append to a listbuffer which is a value of a mutable map in Scala?
body: <pre><code>val mymap= collection.mutable.Map.empty[String,Seq[String]]
  mymap("key") = collection.mutable.ListBuffer("a","b")
  mymap.get("key") += "c"
  </code></pre>
  
  <p>The last line to append to the list buffer is giving error. How the append can be done ?</p>