[torch api] Support down conversion of opsets

[justinchuby]

Starting from PyTorch 2.9, down conversion is turned on and supported.

[Copilot]

Pull Request Overview

This PR adds support for down conversion of ONNX opsets starting from PyTorch 2.9, enabling fallback to the ONNX C API when the onnxscript version converter doesn't support the requested conversion.

• Introduces a new PyTorch 2.9 API module with support for version conversion with fallback enabled
• Adds warning logging when fallback conversion is used
• Corrects the docstring in PyTorch 2.8 module from "2.7" to "2.8"

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
onnxscript/version_converter/init.py	Adds warning log when fallback conversion is used
onnxscript/_framework_apis/torch_2_9.py	New module implementing convert_version with fallback support for PyTorch 2.9
onnxscript/_framework_apis/torch_2_8.py	Fixes docstring from "PyTorch 2.7" to "PyTorch 2.8"

[codecov]

❌ 6 Tests Failed:

Tests completed	Failed	Passed	Skipped
14208	6	14202	2067

View the top 3 failed test(s) by shortest run time

onnxscript.backend.onnx_export_test.TestOnnxBackEnd::test_export2python_produces_correct_onnx_script_model_0564_test_log

Stack Traces | 0.003s run time

onnxscript\backend\onnx_export_test.py:132: in extract_functions
    mod = importlib.import_module(import_name)
C:\hostedtoolcache\windows\Python\3.10.11\x64\lib\importlib\__init__.py:126: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
E   ModuleNotFoundError: No module named 'tests.onnx_backend_test_code.test_log'

The above exception was the direct cause of the following exception:
.nox\test\lib\site-packages\parameterized\parameterized.py:620: in standalone_func
    return func(*(a + p.args), **p.kwargs, **kw)
onnxscript\backend\onnx_export_test.py:266: in test_export2python_produces_correct_onnx_script_model
    functions = extract_functions(backend_test.name, code, self.test_folder)
onnxscript\backend\onnx_export_test.py:134: in extract_functions
    raise AssertionError(
E   AssertionError: Unable to import 'tests.onnx_backend_test_code.test_log' (e=No module named 'tests.onnx_backend_test_code.test_log') (file: 'D:\\a\\onnxscript\\onnxscript\\tests\\onnx_backend_test_code\\test_log.py', absolute path: 'D:\\a\\onnxscript\\onnxscript\\tests\\onnx_backend_test_code\\test_log.py', current folder: D:\a\onnxscript\onnxscript
E   ---- CONTENT --
E   import numpy as np
E   from onnx import TensorProto
E   from onnx.helper import make_tensor
E   from onnxscript import script, external_tensor
E   from onnxscript.values import Opset
E   from onnxscript.onnx_types import FLOAT
E   from onnxscript.onnx_opset import opset13
E   
E   @script()
E   def bck_test_log(x: FLOAT[3,4,5]) -> (FLOAT[3,4,5]):
E       y = opset13.Log(x)
E       return y

onnxscript.backend.onnx_export_test.TestOnnxBackEnd::test_export2python_produces_correct_onnx_script_model_0759_test_or_bcast4v4d

Stack Traces | 0.003s run time

onnxscript\backend\onnx_export_test.py:132: in extract_functions
    mod = importlib.import_module(import_name)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
C:\hostedtoolcache\windows\Python\3.11.9\x64\Lib\importlib\__init__.py:126: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
E   ModuleNotFoundError: No module named 'tests.onnx_backend_test_code.test_or_bcast4v4d'

The above exception was the direct cause of the following exception:
.nox\test\Lib\site-packages\parameterized\parameterized.py:620: in standalone_func
    return func(*(a + p.args), **p.kwargs, **kw)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript\backend\onnx_export_test.py:266: in test_export2python_produces_correct_onnx_script_model
    functions = extract_functions(backend_test.name, code, self.test_folder)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript\backend\onnx_export_test.py:134: in extract_functions
    raise AssertionError(
E   AssertionError: Unable to import 'tests.onnx_backend_test_code.test_or_bcast4v4d' (e=No module named 'tests.onnx_backend_test_code.test_or_bcast4v4d') (file: 'D:\\a\\onnxscript\\onnxscript\\tests\\onnx_backend_test_code\\test_or_bcast4v4d.py', absolute path: 'D:\\a\\onnxscript\\onnxscript\\tests\\onnx_backend_test_code\\test_or_bcast4v4d.py', current folder: D:\a\onnxscript\onnxscript
E   ---- CONTENT --
E   import numpy as np
E   from onnx import TensorProto
E   from onnx.helper import make_tensor
E   from onnxscript import script, external_tensor
E   from onnxscript.values import Opset
E   from onnxscript.onnx_types import BOOL
E   from onnxscript.onnx_opset import opset7
E   
E   @script()
E   def bck_test_or_bcast4v4d(x: BOOL[1,4,1,6], y: BOOL[3,1,5,6]) -> (BOOL[3,4,5,6]):
E       r_or = opset7.Or(x, y)
E       return r_or

onnxscript.backend.onnx_export_test.TestOnnxBackEnd::test_export2python_produces_correct_onnx_script_model_1099_test_shape_clip_start

Stack Traces | 0.003s run time

onnxscript\backend\onnx_export_test.py:132: in extract_functions
    mod = importlib.import_module(import_name)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
C:\hostedtoolcache\windows\Python\3.11.9\x64\Lib\importlib\__init__.py:126: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
E   ModuleNotFoundError: No module named 'tests.onnx_backend_test_code.test_shape_clip_start'

The above exception was the direct cause of the following exception:
.nox\test\Lib\site-packages\parameterized\parameterized.py:620: in standalone_func
    return func(*(a + p.args), **p.kwargs, **kw)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript\backend\onnx_export_test.py:266: in test_export2python_produces_correct_onnx_script_model
    functions = extract_functions(backend_test.name, code, self.test_folder)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript\backend\onnx_export_test.py:134: in extract_functions
    raise AssertionError(
E   AssertionError: Unable to import 'tests.onnx_backend_test_code.test_shape_clip_start' (e=No module named 'tests.onnx_backend_test_code.test_shape_clip_start') (file: 'D:\\a\\onnxscript\\onnxscript\\tests\\onnx_backend_test_code\\test_shape_clip_start.py', absolute path: 'D:\\a\\onnxscript\\onnxscript\\tests\\onnx_backend_test_code\\test_shape_clip_start.py', current folder: D:\a\onnxscript\onnxscript
E   ---- CONTENT --
E   import numpy as np
E   from onnx import TensorProto
E   from onnx.helper import make_tensor
E   from onnxscript import script, external_tensor
E   from onnxscript.values import Opset
E   from onnxscript.onnx_types import FLOAT, INT64
E   from onnxscript.onnx_opset import opset21
E   
E   @script()
E   def bck_test_shape_clip_start(x: FLOAT[3,4,5]) -> (INT64[3]):
E       y = opset21.Shape(x, start=-10)
E       return y

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