docs: def unrank(n, sequence=string.ascii_lowercase):
      """Unrank n from sequence in colexicographical order.
  
      >>> [''.join(unrank(i)) for i in range(8)]
      ['', 'a', 'b', 'ab', 'c', 'ac', 'bc', 'abc']
  
      >>> unrank(299009)
      ['a', 'm', 'p', 's']
      """
      return list(map(sequence.__getitem__, indexes(n)))