code: def start_fetching_next_page(self):
          
          if not self._paging_state:
              raise QueryExhausted()
  
          self._make_query_plan()
          self.message.paging_state = self._paging_state
          self._event.clear()
          self._final_result = _NOT_SET
          self._final_exception = None
          self._start_timer()
          self.send_request()
docs: If there are more pages left in the query result, this asynchronously
          starts fetching the next page.  If there are no pages left, :exc:`.QueryExhausted`
          is raised.  Also see :attr:`.has_more_pages`.
  
          This should only be called after the first page has been returned.
  
          .. versionadded:: 2.0.0