System information (version)

• OpenCV =>4.30.
• Operating System / Platform =>Ubuntu 18.04
• Compiler =>Qt5

Detailed description

There may be a bug in importing an 'Expand' layer.

It can be reproduced with the network in #17516 (comment).
Set the 'state' as an input of 'forward':

def forward(self, x, state):

then, delete:

state = torch.zeros(1, self.sDim)

In this manner, it will be copied and concatenated.
I think there may be a bug, because the name of the 'concat' layer is the same with the last copy of input.
I think we should add

node_proto.set_output(0, layerParams.name);

after

If not, it will throw an exception in the following steps, because the concat layer can not be found with a wrong name.

Steps to reproduce

It is described above.

Issue submission checklist

• I report the issue, it's not a question
• I checked the problem with documentation, FAQ, open issues,
  answers.opencv.org, Stack Overflow, etc and have not found solution
• I updated to latest OpenCV version and the issue is still there
• There is reproducer code and related data files: videos, images, onnx, etc