title: How do you extend an existing module?
body: <p>In C#, it would look like this:</p>
  
  <pre><code>namespace QuartzCore {
      // extensions
  
      namespace Metal {
        // extensions
      }
  }
  </code></pre>
  
  <p>or even</p>
  
  <pre><code>namespace QuartCore.Metal { extensions }
  </code></pre>