input: 
  def get_max_value(numbers):
      """Return the largest value from a given list of numbers.
      >>> get_max_value([2, 4, 1, 6])
      6
      >>> get_max_value([10, 3, 8, 5])
      10
      """
      return max(numbers)
  
output:     
      if not numbers:
          return None
  