input: Write a python function to print even numbers from a given list.
  assert print_even_numbers([2, 4, 7, 14, 21]) == "2 4 14 "
  assert print_even_numbers([1, 3, 5, 8, 10, 13]) == "8 10 "
  assert print_even_numbers([11, 22, 33, 44, 55, 66]) == "22 44 66 "
output: def print_even_numbers(lst):
      result = ""
      for num in lst:
          if num % 2 == 0:
              result += str(num) + " "
      return result