title: Making a code that will add unique characters to a list
body: <p>so the below code should be talking the unique characters in msg and the unique characters and making a list containing two sublists. An example would be </p>
  
  <pre><code>crack_the_code('hello there', 'abccd eabfb') 
  </code></pre>
  
  <p>should return                </p>
  
  <pre><code>[['h', 'e', 'l', 'o', 't', 'r'], ['a', 'b', 'c', 'd', 'e', 'f']].
  </code></pre>
  
  <p>What I have tried to do below is made three lists and then ran a for loop to check if i is in the new list (unique) if not adds it to the list, same was done for unique_code. </p>
  
  <p>Then finally put the two lists together and returned but when I print I get none. Any help would be appreciated. </p>
  
  <pre><code>def crack_the_code(msg, code):
      unique = []
      unique_code = []
      cracked = []
      for i in msg:
          if i not in unique:
              unique.extend(i)
      for item in code:
          if item not in unique_code:
              unique_code.extend(item)
      cracked = unique.append(unique_code)
      return cracked
  
  print(crack_the_code('hello there', 'abcd eabfb'))
  </code></pre>