input: Write a python function to add 2 to each element of a list.
  assert add_two([1, 2, 3, 4]) == [3, 4, 5, 6]
  assert add_two([0, -1, -2]) == [2, 1, 0]
  assert add_two([10, 20, 30]) == [12, 22, 32]
output: def add_two(lst):
      return [x + 2 for x in lst]