code: def fetch_next_page(self):
          
          if self.response_future.has_more_pages:
              self.response_future.start_fetching_next_page()
              result = self.response_future.result()
              self._current_rows = result._current_rows  # ResultSet has already _set_current_rows to the appropriate form
          else:
              self._current_rows = []
docs: Manually, synchronously fetch the next page. Supplied for manually retrieving pages
          and inspecting :meth:`~.current_page`. It is not necessary to call this when iterating
          through results; paging happens implicitly in iteration.