input: Write a function to find the longest word in a sentence.
  assert find_longest_word("This is a sample sentence") == "sentence"
  assert find_longest_word("Python programming language") == "programming"
  assert find_longest_word("Write a function to find the longest word") == "function"
output: def find_longest_word(sentence):
      words = sentence.split()
      longest_word = max(words, key=len)
      return longest_word