input: Write a function to identify the longest word in a given sentence. If there is a tie for the longest word, return the first one encountered. For simplicity, assume the sentence only contains letters, spaces, and punctuation marks.
  assert find_longest_word("The rain in Spain stays mainly in the plain.") == "mainly"
  assert find_longest_word("I love programming in Python") == "programming"
  assert find_longest_word("Short words are okay too") == "words"
  assert find_longest_word("A") == "A"
  assert find_longest_word("") == ""
output: def find_longest_word(sentence):
      words = sentence.split()
      if not words:
          return ""
      longest_word = words[0]
      for word in words:
          if len(word) > len(longest_word):
              longest_word = word
      return longest_word