input: Write a function to identify the longest word in a given sentence. The function should split the sentence into individual words, iterate over each word to find the longest one, and then return the longest word. If there are multiple words with the same length, the function should return the first one it finds.
  assert find_longest_word("The rain in Spain stays mainly in the plain.") == "mainly"
  assert find_longest_word("Python is a powerful programming language.") == "programming"
  assert find_longest_word("") == ""
  assert find_longest_word("A sentence with multiple words of the same length.") == "sentence"
  assert find_longest_word("One") == "One"
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