title: converting 3d lists to 2d lists in python
body: <p>I have an array like <br></p>
  
  <pre><code>sets=[ [ ['a', 'c'] , ['a', 'e'] ] , [ ['b', 'c'] , ['b', 'e'] ] , [ ['a','z'] ] ]
  </code></pre>
  
  <p>I wanted the reduced dimension of list and remove common element in the innerlists </p>
  
  <p>My expected output is </p>
  
  <pre><code>[['a','c','e'] , ['b','c','e'] , ['a','z'] ]
  </code></pre>