input: Write a function to sort words in a given string by their length in decreasing alphabetical order. The function should take a string as input and return the sorted string. If the input string is empty, the function should return an empty string.
  assert sort_words_by_length_and_alphabetical("This is the string which is to be sorted")=="which to This the string sorted is be"
  assert sort_words_by_length_and_alphabetical("The quick brown fox jumps over the lazy dog")=="quick jumps The brown over fox lazy dog the"
  assert sort_words_by_length_and_alphabetical("")==""
  assert sort_words_by_length_and_alphabetical("singleword")=="singleword"
  assert sort_words_by_length_and_alphabetical("a an the")=="the a an"
output: def sort_words_by_length_and_alphabetical(s):
      if not s:
          return ""
      words = s.split()
      words.sort(key=lambda x: (-len(x), x))
      return " ".join(words)