ONNX: textual syntax support

[AlexHJH]

noticed that .onnxtxt suffix has bin registered in the recent commit, will it be completely supported in the future?

network file like this

[lutzroeder]

The .pbtxt format is already supported. The example posted is not a valid Text Protocol Buffer for ONNX though.

import onnx
model = onnx.load('example.onnx')
file = open('example.pbtxt', 'w')
text = str(model);
file.write(text)
file.close()

[AlexHJH]

onnx has a new feature
(https://github.com/onnx/onnx/blob/main/docs/Syntax.md)
The syntax enables a compact and readable representation of ONNX models，like prototxt in caffe

[AlexHJH]

@lutzroeder so i think it is possible to describe the onnx network in a textual way，and visualize it

[lutzroeder]

@AlexHJH can you share a few more complex example files?

.onnxtxt should not be used for such files since it is already being used for ONNX files in .pbtxt format.

[gramalingam]

@AlexHJH : please note that the syntax you describe is an experimental feature of ONNX (as mentioned in the documentation). You can use the parser documented there (in C++ or python) to create a standard .onnx protobuf file which can be consumed by Netron or any other tool. It is not meant to be an interchange standard at this point, just a tool to help users easily create onnx protobuf files.

[AlexHJH]

i think it a very good idea to describe the model in a textual syntax, but few people know it now. in the past, i wanted to modify onnx model but hvae to go back to the code and reorganize them, maybe just a little change. but now i can modify it on the text directly after i convert it to text representation, i tried and it really work @gramalingam

[lutzroeder]

Duplicate of #884