Add clamp() step to PrePostProcessor Python API

[lawrencedsz9]

Details:

This PR adds the clamp functionality ( clamp(min, max) ) , as a built-in preprocessing and postprocessing step as requested in the issue.
Added python bindings for PreProcessorSteps.clamp(min, max) and PostProcessor steps as well in the pre_post_process.cpp file.
Also added Python unit tests covering preprocessing clamp , chained operations(like mean/scale + clamp), and the postprocessing clamp.
The C++ implementation (ov::op::v0::Clamp) was already present. This PR exposes it to Python users via the API.

Tickets:

• [Feature Request]: Add clamp functionality to input.preprocess #23001

AI Assistance:

i have used AI assistance.
I had used copilot to get an understanding of the codebase and existing C++ structure. All the code was reviewed and i had validated manually by building pyopenvino target locally. I had run the C++ unit tests , with getting all 13 tests passed as well as with manual test that confirms the Clamp node appears in the model graph.

[Copilot]

Pull request overview

This PR exposes the existing C++ ov::preprocess::PreProcessSteps::clamp() and ov::preprocess::PostProcessSteps::clamp() APIs to Python users by adding pybind11 bindings for both, along with Python unit tests. The underlying C++ implementation was already present; this PR makes it accessible via the Python PrePostProcessor API.

Changes:

• Added clamp(min_value, max_value) binding to PreProcessSteps Python API with docstring
• Added clamp(min_value, max_value) binding to PostProcessSteps Python API with docstring
• Added three Python unit tests: preprocessing clamp, chained mean/scale + clamp, and postprocessing clamp

Reviewed changes

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

File	Description
src/bindings/python/src/pyopenvino/graph/preprocess/pre_post_process.cpp	Adds pybind11 .def("clamp", ...) for both PreProcessSteps and PostProcessSteps, delegating to the already-implemented C++ API
src/bindings/python/tests/test_graph/test_preprocess.py	Adds three tests verifying the Clamp node appears in the built model for preprocessing, chained preprocessing, and postprocessing scenarios

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Issues found:

1. [HIGH] Missing .pyi stub update (src/bindings/python/src/openvino/_pyopenvino/preprocess.pyi): The clamp method is not added to the type stub for either PreProcessSteps or PostProcessSteps. This file is manually maintained and shipped with the wheel — its pad method was added when that binding was introduced. Without this update, users relying on type checkers (mypy, pyright) or IDE autocompletion will see "undefined attribute" errors for the new API.

2. [LOW] Inconsistent test function name: The new postprocessing test is named test_graph_postprocess_clamp (line 839), but the established convention in the file prefixes all tests — including postprocessing ones — with test_graph_preprocess_* (e.g., test_graph_preprocess_output_postprocess, test_graph_preprocess_postprocess_layout). It should be renamed to test_graph_preprocess_postprocess_clamp.

[Copilot]

[HIGH] The clamp method is missing from the Python type stub file src/bindings/python/src/openvino/_pyopenvino/preprocess.pyi for both PreProcessSteps (around line 294) and PostProcessSteps (around line 233). This file is shipped with the wheel and is required for IDE autocompletion and static type checkers (mypy, pyright, etc.) to recognize the new API. For reference, the pad method was added to this same stub file when it was introduced. Without updating this file, users will see "undefined attribute" errors from type checkers when calling .clamp(). Both PreProcessSteps.clamp(self, min_value: float, max_value: float) -> PreProcessSteps and PostProcessSteps.clamp(self, min_value: float, max_value: float) -> PostProcessSteps stubs need to be added.

[lawrencedsz9]

I have addressed these issues and implemented the suggestions and would like for the review.

[Copilot]

[LOW] The test function test_graph_postprocess_clamp uses an inconsistent naming pattern. All other tests in this file that exercise postprocessing functionality follow the test_graph_preprocess_* prefix convention (e.g., test_graph_preprocess_output_postprocess at line 162, test_graph_preprocess_postprocess_layout at line 440). This test should be renamed to test_graph_preprocess_postprocess_clamp for consistency.

Suggested change

	def test_graph_postprocess_clamp():
	def test_graph_preprocess_postprocess_clamp():

[lawrencedsz9]

I have updated the PR to address the initial Copilot review, I have added .pyi type stubs for clamp in both PreProcessSteps and PostProcessSteps and also renamed the preprocessing test.

[almilosz]

Hi, please fix linter check

[lawrencedsz9]

Hi, please fix linter check

I've applied the formatting fixes (linter) and added the missing .pyi stubs as requested. I've force-pushed the updated commit. Please do let me know if any changes need to be done.

[lawrencedsz9]

I have updated the requested changes , would like for the review.

[lawrencedsz9]

Hi @almilosz, thanks for the heads up on the auto-generated .pyi stubs. I've reverted those changes and updated the PR into a single commit containing only the C++ bindings and Python tests. Kindly review this.