input: Write a python function to find the intersection of two lists.
  assert intersection([1, 2, 3, 4], [3, 4, 5, 6]) == [3, 4]
  assert intersection([10, 20, 30], [30, 40, 50]) == [30]
  assert intersection([7, 8, 9], [10, 11, 12]) == []
output: def intersection(list1, list2):
      return [item for item in list1 if item in list2]