For all stacks to be sent, append a pause after each text layer.

async def flush(self, request: Request, stacks: List[Stack]):
        """
        For all stacks to be sent, append a pause after each text layer.
        """

        ns = await self.expand_stacks(request, stacks)
        ns = self.split_stacks(ns)
        ns = self.clean_stacks(ns)

        await self.next(request, [Stack(x) for x in ns])