def insert_empty(self, tk, before=True):
            """ Insert an Empty Token into token list - before or after tk. """
            if not (0 < tk.pos < (len(self) - 1)):
                return False
            ptk = self[tk.pos - 1]
            ntk = self.formatter.CharacterData(self, [" "])
            ntk.level = max(ptk.level, tk.level)
            ntk.descendant_mixed = tk.descendant_mixed
            ntk.preserve = ptk.preserve * tk.preserve
            ntk.cdata_section = ptk.cdata_section or tk.cdata_section
            if before:
                self._list.insert(tk.pos + 1, ntk)
            else:
                self._list.insert(tk.pos, ntk)
            for i in range((tk.pos - 1), len(self._list)):
                self._list[i].pos = i