input: Write a python function to reverse the order of words in a given sentence and return them as a list.
  assert reverse_words('This is an example sentence') == ['sentence', 'example', 'an', 'is', 'This']
  assert reverse_words('Hello world') == ['world', 'Hello']
  assert reverse_words('') == []
output: def reverse_words(sentence):
      return sentence.split()[::-1]