input: Write a function to reverse the order of words in a given string. The function should return the string with words in the reversed order. If the input string is empty, the function should return an empty string.
  assert reverse_words("Hello world this is a test")=="test a is this world Hello"
  assert reverse_words("SingleWordInput")=="SingleWordInput"
  assert reverse_words("")==""
  assert reverse_words("  Multiple spaces     between words  ")=="words between spaces Multiple"
  assert reverse_words("EndsWithSpace ")== "EndsWithSpace"
output: def reverse_words(s):
      words = s.split()
      reversed_words = words[::-1]
      return ' '.join(reversed_words)