input: from typing import List, Tuple
  
  def min_max(arr: List[int]) -> Tuple[int, int]:
      """ Return the greatest and smallest values from a given array of numbers.
      >>> 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)