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, split it into words, sort the words based on their length (in descending order) and then by alphabetical order if lengths are the same, and return the sorted string. If the input string is empty, it should return an empty string.
  def sort_words_by_length_and_alphabet(my_string):
      if not my_string:
          return ""
      words = my_string.split(' ')
      words_with_length = [(len(word), word) for word in words]
      words_with_length.sort(key=lambda x: (-x[0], x[1]))
      sorted_string = " ".join([i[1] for i in words_with_length])
      return sorted_string
  
  assert sort_words_by_length_and_alphabet("This is the string which is to be sorted")=="which is the sorted string to be This"
  assert sort_words_by_length_and_alphabet("apple banana orange pear")=="banana orange apple pear"
  assert sort_words_by_length_and_alphabet("a an the and")=="the and an a"
  assert sort_words_by_length_and_alphabet("")==""
output: def sort_words_by_length_and_alphabet(my_string):
      if not my_string:
          return ""
      words = my_string.split(' ')
      words_with_length = [(len(word), word) for word in words]
      words_with_length.sort(key=lambda x: (-x[0], x[1]))
      sorted_string = " ".join([i[1] for i in words_with_length])
      return sorted_string