input: Write a function to identify the longest word in a given sentence. Return the longest word. If multiple words have the same maximum length, return the first one encountered.
  assert find_longest_word("The rain in Spain stays mainly in the plain.")=='mainly'
  assert find_longest_word("Python is a high-level programming language.")=='programming'
  assert find_longest_word("I love coding in Python.")=='coding'
  assert find_longest_word("This is a simple test.")=='simple'
  assert find_longest_word("One two three.")=='three'
output: def find_longest_word(sentence):
      words = sentence.split()
      longest_word = max(words, key=len)
      return longest_word