input: Write a function to extract words longer than 3 characters from a string.
  assert extract_long_words("This is a test string with some long words") == ["This", "test", "string", "with", "some", "long", "words"]
  assert extract_long_words("Short words") == ["Short", "words"]
  assert extract_long_words("Python programming is fun") == ["Python", "programming"]
output: def extract_long_words(s):
      return [word for word in s.split() if len(word) > 3]