input: Write a function to find the intersection of two lists.
  assert intersection([1, 2, 3, 4, 5], [4, 5, 6, 7, 8]) == [4, 5]
  assert intersection([10, 20, 30, 40], [30, 40, 50, 60]) == [30, 40]
  assert intersection([7, 8, 9], [10, 11, 7, 9]) == [7, 9]
output: def intersection(list1, list2):
      return list(set(list1) & set(list2))