title: Remove duplicates from an array of array
body: <p>How do I remove duplicates from this array?</p>
  
  <pre><code>product_areas = [["1", "2", "3"], ["3", "1", "2"]]
  </code></pre>
  
  <p>I have tried <code>product_areas.uniq!</code>, <code>product_area.uniq</code> but the same thing is repeating. What am I missing here?</p>
  
  <p><strong>Expected Output:</strong></p>
  
  <pre><code>product_areas = ["1", "2", "3"]
  </code></pre>