docs: def _unix_word_rubout(text, pos):
      """
      Kill the word behind pos, using white space as a word boundary.
      """
      words = text[:pos].rsplit(None, 1)
      if len(words) < 2:
          return text[pos:], 0
      else:
          index = text.rfind(words[1], 0, pos)
          return text[:index] + text[pos:], index