Find if value exists in multiple lists
<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>