docs: async def execution_barrier(self):
          """Wait for executors to finish.
  
          At least one must finish after this point to avoid a deadlock.
          """
          async def _barrier():
              """Enter the sync block and exit the app afterwards."""
              async with self.sync_counter:
                  pass
              await consumer.exit_consumer()
  
          self._ensure_counter()
          await asyncio.wait([
              _barrier(),
              consumer.run_consumer(),
          ])
          self.sync_counter = self._SynchronizationManagerDummy()