input: def substring_in_order(string: str) -> List[str]:
      """Generates a list of all substrings of the given string in order from the longest to the shortest length.
      >>> substring_in_order('abc')
      ['abc', 'ab', 'bc', 'a', 'b', 'c']
      >>> substring_in_order('test')
      ['test', 'tes', 'est', 'te', 'es', 'st', 't', 'e', 's', 't']
      """
output:     substrings = []
      n = len(string)
      for length in range(n, 0, -1):
          for start in range(n - length + 1):
              substrings.append(string[start:start+length])
      return substrings