input: Write a function to generate a list of lists of words from a given list of strings. Each sublist should start with the first word of the corresponding string followed by the subsequent words. If the input list is empty, return an empty list.
  def get_word_lists(strings):
      if not strings:
          return []
      word_lists = []
      for string in strings:
          words = string.split(" ")
          word_list = [words[0:i+1] for i in range(len(words))]
          word_lists.append(word_list)
      return word_lists
  
  assert get_word_lists(["Hello world", "This is a test"])==[["Hello"], ["Hello", "world"], ["This"], ["This", "is"], ["This", "is", "a"], ["This", "is", "a", "test"]]
  assert get_word_lists([])==[]
  assert get_word_lists(["Single"])==[["Single"]]
output: def get_word_lists(strings):
      if not strings:
          return []
      word_lists = []
      for string in strings:
          words = string.split(" ")
          word_list = [words[0:i+1] for i in range(len(words))]
          word_lists.append(word_list)
      return word_lists