input: Write a python function to reverse the order of words in a sentence.
  assert reverse_sentence("sentence. a is This") == "This is a sentence."
  assert reverse_sentence("Hello World") == "World Hello"
  assert reverse_sentence("Python is fun") == "fun is Python"
output: def reverse_sentence(sentence):
      words = sentence.split()
      reversed_words = words[::-1]
      return ' '.join(reversed_words)