input: Write a function to find unique elements in two lists.
  assert find_unique_elements([1, 2, 3, 4], [3, 4, 5, 6]) == ([1, 2], [5, 6])
  assert find_unique_elements([10, 20, 30], [20, 40, 50]) == ([10, 30], [40, 50])
  assert find_unique_elements([7, 8, 9], [9, 10, 11]) == ([7, 8], [10, 11])
output: def find_unique_elements(list1, list2):
      set1 = set(list1)
      set2 = set(list2)
      unique_in_list1 = list(set1 - set2)
      unique_in_list2 = list(set2 - set1)
      return unique_in_list1, unique_in_list2