Consider a set S of n elements, {a1, a2, …, an}., the power set of S, denoted P(S), is the set of all subsets of S. We know that there are 2n subsets of S, counting the empty set . Write a function powerSet(s) that returns the power set of s. You can represent the sets using Python lists. The empty set can be represented with the empty list, []. The powerSet function should return a list of lists. For example, calling powerSet([1, 2]) should return something like [ [], [1], [2], [1, 2] ].