title: Creating a yaml file with aliases through PyYAML
body: <p>I need to create a yaml file with the following format:</p>
  
  <pre><code>imager: &amp;imager
    type: "detector"
    half_angle: 75 degrees
    max_distance: 23000 meters
  ownship: &amp;ownship
    origin: [11,11,5]
    type: "uav"
  
  vehicles:
    - &lt;&lt;: *ownship
    name: "uav1"
    origin: [35.69257148103399 degrees, -117.689417544709 degrees, 5500]
    sensors:
      - &lt;&lt;: *imager
        name: "imager1"
  </code></pre>
  
  <p>I have all the specific data stored in Python classes, so I figured I'd use PyYAML to make things easy.  However, when I went to read the documentation, I saw no mention of how to handle aliases with PyYAML.  Does this functionality exist, or should I just go ahead and make my own yaml writer?   </p>