input: 
  def get_max_value(numbers):
      """Prints the largest value from a given list of numbers.
      >>> get_max_value([2, 4, 1, 6])
      6
      >>> get_max_value([10, 5, 7, 1])
      10
      """
      return max(numbers)
  
output:     if not numbers:
          return None
      max_value = numbers[0]
      for num in numbers:
          if num > max_value:
              max_value = num
      return max_value