title: In a tree data structure, is a node a sibling of itself?
body: <p>I am building a tree like data structure.  What is the expected behavior if I have a method</p>
  
  <pre><code>public Set getSiblingNodes(Node node);
  </code></pre>
  
  <p>Should this method return a set including or excluding itself?</p>
  
  <p>Thanks!</p>