input: 
  def get_greatest_2(items: List[int]) -> Tuple[int, int]:
      """
      Return the two greatest numbers in a given list of integers.
  
      >>> get_greatest_2([1, 5, 3, 7, 4, 7, 8, 9, 2, 10, 6, 8])
      (10, 9)
      """
  
output:     if len(items) < 2:
          raise ValueError("List must contain at least two elements")
      
      first = second = float('-inf')
      
      for num in items:
          if num > first:
              second = first
              first = num
          elif num > second:
              second = num
      
      return (first, second)