title: How to remove duplicates from a two-dimensional array?
body: <p>I have a two-dimensional array:</p>
  <pre><code>[[7,3], [7,3], [3,8], [7,3], [7,3], [1,2]]
  </code></pre>
  <p>Is there any smart way to remove duplicated elements from this?
  It should return such array:</p>
  <pre><code>[[7,3], [3,8], [1,2]]
  </code></pre>
  <p>Thanks!</p>