input: Write a function to take a list of strings and generate a list of lists of words from the strings. The returned list should have the first word for each string followed by following words for each string. If the list of strings is empty, return an empty list.
  assert get_word_lists(["Hello world", "This is a test"])==[["Hello", "world"], ["This", "is", "a", "test"]]
  assert get_word_lists([])==[]
output: def get_word_lists(strings):
      if not strings:
          return []
      result = []
      for s in strings:
          result.append(s.split())
      return result