code: func Raw(want []byte) NetworkChecker {
  	return func(t *testing.T, h []header.Network) {
  		t.Helper()
  
  		if got := h[len(h)-1].Payload(); !reflect.DeepEqual(got, want) {
  			t.Errorf("Wrong payload, got %v, want %v", got, want)
  		}
  	}
  }
docs: // Raw creates a checker that checks the bytes of payload.
  // The checker always checks the payload of the last network header.
  // For instance, in case of IPv6 fragments, the payload that will be checked
  // is the one containing the actual data that the packet is carrying, without
  // the bytes added by the IPv6 fragmentation.