input: Write a function to iterate over a list of numbers and print only the even numbers. If the list is empty, the function should do nothing.
  assert print_even_numbers([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) is None
  assert print_even_numbers([]) is None
  assert print_even_numbers([2, 4, 6, 8, 10]) is None
  assert print_even_numbers([1, 3, 5, 7, 9]) is None
  assert print_even_numbers([1, 2, 3, 4, 5, 7, 9, 11, 13]) is None
output: def print_even_numbers(numbers):
      for num in numbers:
          if num % 2 == 0:
              print(num)