title: How add a list inside a map in kotlin
body: <p>I need to add some <code>MutableList&lt;String&gt;</code> to a map <code>Map&lt;String, List&lt;String&gt;&gt;</code>, here is how I tried to initialize it :</p>
  
  <pre><code>    private var theSteps: MutableList&lt;String&gt; = mutableListOf()
      private var optionsList: Map&lt;String, List&lt;String&gt;&gt; = mapOf()
  </code></pre>
  
  <p>Then I add data to the `MutableList this way :</p>
  
  <pre><code>        theSteps.add("one")
          theSteps.add("two")
          theSteps.add("three")
  </code></pre>
  
  <p>everything works fine untill i try to add to the <code>Map</code>:</p>
  
  <p><code>optionsList.add("list_1" to theSteps)</code></p>
  
  <p>It just gives me the error <code>Unresolved reference add</code> and I can't find clear documentation about how to add items to it.</p>