title: List of objects with a unique attribute
body: <p>I have a list of objects that each have a specific attribute.  That attribute is not unique, and I would like to end up with a list of the objects that is a subset of the entire list such that all of the specific attributes is a unique set.</p>
  
  <p>For example, if I have four objects:</p>
  
  <pre><code>object1.thing = 1
  object2.thing = 2
  object3.thing = 3
  object4.thing = 2
  </code></pre>
  
  <p>I would want to end up with either </p>
  
  <pre><code>[object1, object2, object3]
  </code></pre>
  
  <p>or </p>
  
  <pre><code>[object1, object3, object4]
  </code></pre>
  
  <p>The exact objects that wind up in the final list are not important, only that a list of their specific attribute is unique.</p>
  
  <p>EDIT: To clarify, essentially what I want is a set that is keyed off of that specific attribute.</p>