input: def min_max(numbers: List[float]) -> List[float]:
      """ This function takes an array of numbers and returns an array with the greatest and smallest values.
      >>> min_max([3, 4, 2, 8, 15, 6])
      [2, 15]
      """
  
      min_val = min(numbers)
      max_val = max(numbers)
      return [min_val, max_val]
output:     min_val = min(numbers)
      max_val = max(numbers)
      return [min_val, max_val]