code: func (s *Stack) UnregisterTransportEndpoint(nicID tcpip.NICID, netProtos []tcpip.NetworkProtocolNumber, protocol tcpip.TransportProtocolNumber, id TransportEndpointID, ep TransportEndpoint) {
  	if nicID == 0 {
  		s.demux.unregisterEndpoint(netProtos, protocol, id, ep)
  		return
  	}
  
  	s.mu.RLock()
  	defer s.mu.RUnlock()
  
  	nic := s.nics[nicID]
  	if nic != nil {
  		nic.demux.unregisterEndpoint(netProtos, protocol, id, ep)
  	}
  }
docs: // UnregisterTransportEndpoint removes the endpoint with the given id from the
  // stack transport dispatcher.