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_alpha("This is the string which is to be sorted")=="which string the sorted is to be is This"
  assert sort_words_by_length_and_alpha("Python is awesome")=="awesome Python is"
  assert sort_words_by_length_and_alpha("a an be in to")=="an be to a in"
  assert sort_words_by_length_and_alpha("")==""
output: def sort_words_by_length_and_alpha(s):
      if not s:
          return ""
      words = s.split()
      words.sort(key=lambda x: (-len(x), x))
      return " ".join(words)