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.
  assert sort_words_by_length("This is the string which is to be sorted")=="which string sorted to is This be the"
  assert sort_words_by_length("apple banana cherry")=="cherry banana apple"
  assert sort_words_by_length("a an the")=="the an a"
  assert sort_words_by_length("hello world")=="world hello"
  assert sort_words_by_length("")==""
output: def sort_words_by_length(s):
      return ' '.join(sorted(s.split(), key=lambda x: (-len(x), x)))