input: def get_word_lists(strings):
      """Generate a list of lists of words from the strings. The returned list should 
      have the first word for each string followed by the following words for each 
      string.
      >>> get_word_lists(["Hello world", "This is a test"])
      [['Hello', 'world'], ['This', 'is', 'a', 'test']]
      """
output:     word_lists = []
      for s in strings:
          words = s.split()
          word_lists.append(words)
      return word_lists