input: def substring_in_order(string: str) -> List[str]:
      """ Takes a string and returns all its substrings in order from longest to shortest length.
      >>> substring_in_order('abc')
      ['abc', 'ab', 'bc', 'a', 'b', 'c']
      >>> substring_in_order('hello')
      ['hello', 'hell', 'ello', 'hel', 'ell', 'llo', 'he', 'el', 'll', 'lo', 'h', 'e', 'l', 'l', 'o']
      """
output:     substrings = []
      for length in range(len(string), 0, -1):
          for start in range(len(string) - length + 1):
              substrings.append(string[start:start + length])
      return substrings