docs: def scale(arr, mn=0, mx=1):
      """
      Apply min-max scaling (normalize)
      then scale to (mn,mx)
      """
      amn = arr.min()
      amx = arr.max()
      # normalize:
      arr = (arr - amn) / (amx - amn)
      # scale:
      if amn != mn or amx != mx:
          arr *= mx - mn
          arr += mn
      return arr