title: How do you return repeats in a 3d list?
body: <p>I have a crazy 3d list that I would like to return the all repeats or appear frequently in my 3d list but I dont know what code to write. </p>
  
  <p>For example Heres my 3d list below</p>
  
  <pre><code>df = [[[10,16,25],[5,12,15],[7,12,25]],[[5,10,17],[15,20],[21,25,30],[10,17]],[[2,7],[4,8,10]],[[16,17,21],[17,32,41],[17,20],[22,24,41]]]
  </code></pre>
  
  <p>I would like my result to be like this</p>
  
  <pre><code>df1 = [[[12],[25]],[[10],[17],[[ ]],[[17],[41]]]
  </code></pre>