input: Write a python function to delete odd numbers from a list.
  assert delete_odd_numbers([1, 2, 3, 4, 5, 6]) == [2, 4, 6]
  assert delete_odd_numbers([10, 21, 34, 47, 56, 69]) == [10, 34, 56]
  assert delete_odd_numbers([11, 13, 15, 18, 20, 25]) == [18, 20]
output: def delete_odd_numbers(lst):
      return [num for num in lst if num % 2 == 0]