docs: def unsort(self, array):
          """
          "Unsorts" given array (restores original order of elements before
          dataset was sorted by sequence length).
  
          :param array: array to be "unsorted"
          """
          if self.sorted:
              inverse = sorted(enumerate(self.indices), key=itemgetter(1))
              array = [array[i[0]] for i in inverse]
          return array