[ONNX] Expose the testing module (#162495)

* Created a new module `torch/onnx/testing.py` that exposes the `assert_onnx_program` function for testing exported ONNX models.
* Updated the ONNX documentation (`docs/source/onnx.md`) to include `onnx_testing` in the list of relevant modules.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/162495
Approved by: https://github.com/titaiwangms, https://github.com/xadupre

docs/source/onnx.md

@@ -102,6 +102,7 @@ also be interested in reading our [development wiki](https://github.com/pytorch/
     onnx_export
     onnx_ops
     onnx_verification
+    onnx_testing
 ```
 
 ### Deprecated APIs

docs/source/onnx_testing.md

@@ -0,0 +1,9 @@
+# torch.onnx.testing
+
+```{eval-rst}
+.. automodule:: torch.onnx.testing
+```
+
+```{eval-rst}
+.. autofunction:: torch.onnx.testing.assert_onnx_program
+```

torch/onnx/testing.py

@@ -0,0 +1,8 @@
+"""Utilities to aid in testing exported ONNX models."""
+
+__all__ = ["assert_onnx_program"]
+
+from torch.onnx._internal.exporter._testing import assert_onnx_program
+
+
+assert_onnx_program.__module__ = "torch.onnx.testing"