def METHOD_NAME(functions: Sequence[values.OnnxFunction], filename: str) -> None:
    # Since we don't yet have LibProto defined, we use a ModelProto as a temporary
    # container for the list of functions exported as a library, with an empty graph
    # and dummy opset_imports.
    model = onnx.helper.make_model(
        onnx.GraphProto(),
        functions=[f.to_function_proto() for f in functions],
        producer_name="p2o",
        opset_imports=[onnx.helper.make_opsetid("", 15)],
    )
    onnx.save(model, filename)