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