input: Write a python function to find the longest word in a sentence.
  assert find_longest_word('This is an example sentence with several words in it.') == 'sentence'
  assert find_longest_word('Short sentence') == 'sentence'
  assert find_longest_word('A very very long sentence indeed') == 'sentence'
output: def find_longest_word(sentence):
      words = sentence.split()
      longest_word = max(words, key=len)
      return longest_word