title: PyYaml "include file" and yaml aliases (anchors/references)
body: <p>I had a large YAML file with a massive use of YAML anchors and references, for example:</p>
  
  <pre><code>warehouse:
    obj1: &amp;obj1
      key1: 1
      key2: 2
  specific:
    spec1: 
      &lt;&lt;: *obj1
    spec2:
      &lt;&lt;: *obj1
      key1: 10
  </code></pre>
  
  <p>The file got too large, so I looked for a solution that will allow me split to 2 files: <code>warehouse.yaml</code> and <code>specific.yaml</code>, and to include the <code>warehouse.yaml</code> inside the <code>specific.yaml</code>. I read <a href="http://code.activestate.com/recipes/577613-yaml-include-support/" rel="noreferrer">this simple article</a>, which describes how I can use PyYAML to achieve that, but it also says that the merge key(&lt;&lt;) is not supported. </p>
  
  <p>I really got an error:</p>
  
  <blockquote>
    <p>yaml.composer.ComposerError: found undefined alias 'obj1</p>
  </blockquote>
  
  <p>when I tried to go like that.</p>
  
  <p>So, I started looking for alternative way and I got confused because I don't really know much about PyYAML.</p>
  
  <p>Can I get the desired merge key support? Any other solutions for my problem?</p>