title: Find if value exists in multiple lists
body: <p>I have 4 list and each element on the list are unique across the 4 list. How do I find if the value exist in one of the list and return which list it exist? </p>
  
  <p>Example list:</p>
  
  <pre><code>value = 'a'
  a = ['a','b','c']
  b = ['d','e','f']
  d = ['g','h','i']
  c = ['j','k','l']
  </code></pre>
  
  <p>My expected output is the name of the list where the value is found: 
  For the example above my expected output would be:</p>
  
  <p>a</p>