code: async def websocket_accept(self, message, stream_name):
          
          is_first = not self.applications_accepting_frames
          self.applications_accepting_frames.add(stream_name)
          # accept the connection after the first upstream application accepts.
          if is_first:
              await self.accept()
docs: Intercept downstream `websocket.accept` message and thus allow this upsteam application to accept websocket
          frames.