code: def killall(self, exc):
          
          self.connection_exc = exc
          # Set an exception for all others
          for method, futs in self._futures.items():
              for fut in futs:
                  if fut.done():
                      continue
                  fut.set_exception(exc)
          self._futures.clear()
docs: Connection/Channel was closed. All subsequent and ongoing requests
              should raise an error