Allow opset_version to be set explicitly when exporting

[NoRaincheck]

I think it would be nice to explicitly set opset_version when exporting, particularly when a custom/particular Opset is being used and the default opset can't be inferred.

Example:

from onnxscript import script
from onnxscript import opset15 as op
from onnxscript.values import Opset
import numpy as np
from onnxscript import STRING
from onnxruntime import InferenceSession


ai_onnx = Opset("ai.onnx.ml", version=2)

@script(ai_onnx, default_opset = op)
def label_encoder(X: STRING["D"]):
    Y = ai_onnx.LabelEncoder(X, keys_strings=["a", "b", "c"], values_int64s=[0, 1, 2], default_int64=42)
    # Y = Y + 0.0 # to force opset version downgrade
    return Y


print(label_encoder(np.array(["a", "b", "c"])))
session = InferenceSession(label_encoder.to_model_proto(ir_version=10).SerializeToString())

for key, value in {"a": 0, "b": 1, "c": 2}.items():
    assert label_encoder(np.array([key]))[0] == value
    assert session.run(None, {"X": np.array([key])})[0] == value

This currently errors with

Traceback (most recent call last):
  File "/Users/XXX/Development/projects/jet/test_onnxscript_label.py", line 25, in <module>
    session = InferenceSession(label_encoder.to_model_proto(ir_version=10).SerializeToString())
  File "/Users/XXX/Development/projects/jet/.venv/lib/python3.10/site-packages/onnxruntime/capi/onnxruntime_inference_collection.py", line 472, in __init__
    self._create_inference_session(providers, provider_options, disabled_optimizers)
  File "/Users/XXX/Development/projects/jet/.venv/lib/python3.10/site-packages/onnxruntime/capi/onnxruntime_inference_collection.py", line 552, in _create_inference_session
    sess = C.InferenceSession(session_options, self._model_bytes, False, self._read_config_from_model)
onnxruntime.capi.onnxruntime_pybind11_state.Fail: [ONNXRuntimeError] : 1 : FAIL : /Users/runner/work/1/s/onnxruntime/core/graph/model_load_utils.h:56 void onnxruntime::model_load_utils::ValidateOpsetForDomain(const std::unordered_map<std::string, int> &, const logging::Logger &, bool, const std::string &, int) ONNX Runtime only *guarantees* support for models stamped with official released onnx opset versions. Opset 23 is under development and support for this is limited. The operator schemas and or other functionality may change before next ONNX release and in this case ONNX Runtime will not guarantee backward compatibility. Current official support for domain ai.onnx is till opset 22.

To force it to work in the current state, one would have to do:

@script(ai_onnx, default_opset = op)
def label_encoder(X: STRING["D"]):
    Y = ai_onnx.LabelEncoder(X, keys_strings=["a", "b", "c"], values_int64s=[0, 1, 2], default_int64=42)
    Y = Y + 0.0 # to force opset version downgrade/inserted from the to_model_proto call
    return Y

To force the opset to be downgraded, since the default_opset is never called.

Happy to be challenged if there is a better way. I can imagine something weird/unintended might occur if the user sets default_opset to something other than what is defined in @script(..., default_opset=<op>) but that generally shouldn't be a problem?

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 70.39%. Comparing base (dd14682) to head (75baf54).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
onnxscript/irbuilder.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2615   +/-   ##
=======================================
  Coverage   70.39%   70.39%           
=======================================
  Files         222      222           
  Lines       26281    26281           
  Branches     2629     2629           
=======================================
  Hits        18500    18500           
  Misses       6861     6861           
  Partials      920      920           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[justinchuby]

I think this is a reasonable change, thanks.

[justinchuby]

@gramalingam for a second opinion

[justinchuby]

Thanks! Merging now. @gramalingam feel free to add if you have further comments