3. Write a method that takes two collections of characters as a parameters and returns a new Set of distinct elements common between the two collections.
// Give me the intersection of common elements between two data sets.
// ['a', 'a', 'c', 'd'], ['a', 'c']
// -> ['a', 'c']
// ['a', 'a', 'c', 'd'], ['a', 'a', 'c']
// -> ['a','c']