input: def min_max(arr):
      """Returns an array with the smallest and greatest values from the input array.
      >>> min_max([3, 4, 2, 8, 15, 6])
      [2, 15]
      """
      min_val = min(arr)
      max_val = max(arr)
      return [min_val, max_val]
output:     min_val = min(arr)
      max_val = max(arr)
      return [min_val, max_val]