docs: def pre_disconnect(self, sid, namespace):
          """Put the client in the to-be-disconnected list.
  
          This allows the client data structures to be present while the
          disconnect handler is invoked, but still recognize the fact that the
          client is soon going away.
          """
          if namespace not in self.pending_disconnect:
              self.pending_disconnect[namespace] = []
          self.pending_disconnect[namespace].append(sid)