Question

Goal: Learn to implement value$-$returning functions.

Assignment: The sigma function is used in Physics and Cryptography. It calculates the sum of the positive divisors of a given number $n,$ each raised to the power of $z.$

Write a function named sigma that has two integer parameters, $n$ and $z.$ The function should find all the positive integers that are divisors of $n,$ raise each of them to the power of $z,$ and calculate the sum of those values. The function should then return the sum.