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