input: 
  def get_max_min(lst):
      """
      Get the maximum and minimum values in a given list.
      >>> get_max_min([3, 5, 1, 7, 9])
      (1, 9)
      >>> get_max_min([10, -2, 0, 23, 15])
      (-2, 23)
      """
      min_value = lst[0]
      max_value = lst[0]
      
      for i in range(1, len(lst)):
          if lst[i] > max_value:
              max_value = lst[i]
          if lst[i] < min_value:
              min_value = lst[i]
      
      return (min_value, max_value)
  
output:     min_value = lst[0]
      max_value = lst[0]
      
      for i in range(1, len(lst)):
          if lst[i] > max_value:
              max_value = lst[i]
          if lst[i] < min_value:
              min_value = lst[i]
      
      return (min_value, max_value)