For python 3 please

Write a function all_strings which takes as input a string alphabet without duplicate characters and a non-negative integer n and which returns a list consisting of all strings (without duplicates!) s of length n such that each character in s belongs to alphabet . For example: all_strings('A', 0) should return [] . all_strings('A', 1) should return ['A'] . all_strings('A', 2) should return ['AA'] . all_strings('AB', 2) should return ['AA', 'AB', 'BA', 'BB'] or some rearrangement of that list. all_strings ('ABC', 2) should return ['AA', 'AB', 'BA', 'BB', 'AC', 'CA', 'C', 'BC', 'CB'] or some rearrangement of that list. all_strings('AB', 3) should return ['AAA', 'AAB', 'ABA', 'ABB', 'BAA', 'BAB', 'BBA', 'BBB'] or some rearrangement of that list. Hint. Recursion