System information (version)

• OpenCV => :4.4:
• Operating System / Platform => :Linux:
• Compiler => :None:

Detailed description

I have trained a simple lstm model use keras, ans then I use keras2onnx to convert keras h5 model to onnx model. Finally, I use opencv 4.4 readNetFromONNX to load the model, but I got the error:
/opencv/modules/dnn/src/onnx/onnx_importer.cpp: error: (-213: The function/feature is not implemented) Unexpected attribute type in function 'getLayerParams'
Below is my keras model and onnx model opened with netron.