title: Can't close() map in ChronicleMap
body: <p>According to the documentation, it is good practice to close <a href="https://github.com/OpenHFT/Chronicle-Map/blob/master/docs/CM_Tutorial.adoc#close-chroniclemap" rel="nofollow noreferrer">https://github.com/OpenHFT/Chronicle-Map/blob/master/docs/CM_Tutorial.adoc#close-chroniclemap</a></p>
  
  <p>I can't, for some reason:</p>
  
  <pre><code>Map&lt;String, String&gt; lexicalizationGraph = ChronicleMap
                  .of(String.class, String.class)
                  .name("lexicalizations-chronicle-map")
                  .constantKeySizeBySample("bn:14271053n")
                  .averageValue("average size of value")
                  .entries(1_000_000_000L)
                  .createPersistedTo(file);
  </code></pre>
  
  <p>and then later:</p>
  
  <pre><code>lexicalizationGraph.close();
  </code></pre>
  
  <p>It gives me the following error:</p>
  
  <pre><code>symbol:   method close()
    location: variable lexicalizationGraph of type java.util.Map&lt;java.lang.String,java.lang.String&gt;
  </code></pre>
  
  <p>How do I close it?</p>