How to adjust a Neural Networks metadata

import onnx
onnx_model = onnx.load(onnxModelName)

Add a metadata key (without duplication):

def addMeta(onnx_model, key, value):
    
    for entry in onnx_model.metadata_props:
        if entry.key == key:
            entry.value = value
            return

    meta = onnx_model.metadata_props.add()
    meta.key = key
    meta.value = value  

Save the onnx model to file:

with open(onnxFilePath, "wb") as f:
    f.write(onnx_model.SerializeToString())