title: how can I empty a mutable map (defined by val)?
body: <p>I define a mutable property for my object</p>
  
  <pre><code>object myobject{
    val myMap = mutable.Map[String,mutable.Set[String]]
    def clear {// I don't know what code I must write here for remove all key Values on myMap}
    def add(keyValue:(String,String)){//some code for add a keyValue to mymap}
  }
  </code></pre>