title: Check if a map contains a specific key in Freemarker
body: <p>In Java:</p>
  
  <pre><code>Map&lt;String, Object&gt; model = new HashMap&lt;&gt;();
  Map&lt;String, String&gt; items = new HashMap&lt;&gt;();
  items.put("color", "red");
  model.put("items", items);
  </code></pre>
  
  <p>I now want to include a snippet in my rendered template if <code>items</code> contains the key <code>color</code>.</p>
  
  <pre><code>&lt;#if ???? &gt;
     the map contains a key called color
  &lt;/#if&gt;
  </code></pre>
  
  <p>What do I replace the ???? with?</p>