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 word_sort_by_length_and_alphabet("This is the string which is to be sorted") == "which string sorted to This the is be"
  assert word_sort_by_length_and_alphabet("apple banana cherry") == "banana cherry apple"
  assert word_sort_by_length_and_alphabet("") == ""
  assert word_sort_by_length_and_alphabet("a an the") == "the an a"
  assert word_sort_by_length_and_alphabet("short longest medium") == "longest medium short"
output: def word_sort_by_length_and_alphabet(s):
      if not s:
          return ""
      words = s.split()
      words.sort(key=lambda x: (-len(x), x))
      return " ".join(words)