def close(self):
        """Close this change stream.

        Stops any "async for" loops using this change stream.
        """
        if self.delegate:
            return self._close()

        # Never started.
        future = self._framework.get_future(self.get_io_loop())
        future.set_result(None)
        return future
Close this change stream.

        Stops any "async for" loops using this change stream.