title: Get first value TreeMultiMap
body: <p>im new in GUAVA, and i dont know how to get the first value in my TreeMultiMap order by a personal comparator.</p>
  
  <p>I create a multitreemap like this:</p>
  
  <pre><code>TreeMultimap&lt;String, ClassX&gt; tm = TreeMultimap.create(Ordering.natural(), new    ComparadorX();
  </code></pre>
  
  <p>I want to get the first value, not order by key, instead for Value.
  I read the Javadoc, and says that i have to use Get(Key), but i dont know how to get my first key order by value.</p>
  
  <p>Thanks.</p>