input: Write a python function to find the two maximum numbers in a list.
  assert maximum_two([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) == (10, 9)
  assert maximum_two([10, 20, 45, 67, 84, 93]) == (93, 84)
  assert maximum_two([5, 7, 9, 8, 6, 4, 3]) == (9, 8)
output: def maximum_two(lst):
      if len(lst) < 2:
          return None
      
      max1 = max2 = float('-inf')
      for num in lst:
          if num > max1:
              max1, max2 = num, max1
          elif num > max2:
              max2 = num
      
      return max1, max2