input: Write a python function to find common elements in two lists.
  assert compare_lists([1, 2, 3, 4], [2, 3, 4, 5]) == [2, 3, 4]
  assert compare_lists([10, 20, 30], [30, 40, 50]) == [30]
  assert compare_lists([1, 2, 3], [4, 5, 6]) == []
output: def compare_lists(list1, list2):
      return list(set(list1) & set(list2))