title: Intersection of two lists including duplicates?
body: <pre><code>&gt;&gt;&gt; a = [1,1,1,2,3,4,4]
  &gt;&gt;&gt; b = [1,1,2,3,3,3,4]
  
  [1,1,2,3,4]
  </code></pre>
  
  <p>Please note this is not the same question as this:
  <a href="https://stackoverflow.com/questions/26663371/python-intersection-of-two-lists-keeping-duplicates">Python intersection of two lists keeping duplicates</a>
  Because even though there are three 1s in list a, there are only two in list b so the result should only have two. </p>