title: How to efficiently iterate a Multimap?
body: <p>I have the following multimap:</p>
  
  <pre><code>Multimap&lt;String,Multimap&lt;String,Integer&gt;&gt;  map =  ArrayListMultimap.create();
  </code></pre>
  
  <p>I need to iterate it, but I am stuck.</p>
  
  <p>How should I iterate it?</p>