[TRTLLM-13028][doc] Add VisualGen API walkthrough example and docs page

[zhenhuaw-me]

Description

Adds a slim, LLM-API-style end-to-end walkthrough of the public VisualGen Python API as examples/visual_gen/api_walkthrough.py, and wires up a "VisualGen Examples" page in the rendered docs that mirrors the LLM Examples page. The example walks through VisualGen.supported_models(), VisualGen.pipeline_config(model), VisualGenArgs(pipeline_config=..., compilation_config=...) with warmup skipped, visual_gen.extra_param_specs, visual_gen.default_params with a num_frames override (plus the matching extra_params override loop — no-op on Wan 2.1, real on Wan 2.2 A14B), and VisualGenOutput.save.

The docs piece scans examples/visual_gen/*.py at Sphinx build time through docs/source/helper.py (same generator that builds the LLM API and trtllm-serve examples pages), produces docs/source/examples/visual_gen_examples.rst, and mounts it between examples/llm_api_examples.rst and examples/trtllm_serve_examples in the Deployment Guide toctree. Existing visual_gen_*.py / .sh CLI scripts without ### :title metadata are temporarily added to helper.py's ignore_list; they can opt in later by adding the metadata block.

The doc structure and the rendered version: https://sc.talos.nvidia.com/view/home/scratch.zhenhuaw_sw/llm/aigv/docs/build/html/index.html

Test Coverage

• New integration test test_visual_gen_api_walkthrough registered in the same L0 lists that already exercise test_visual_gen_quickstart: l0_l40s.yml, l0_gh200.yml, l0_h100.yml, l0_dgx_b200.yml.
• End-to-end verified locally on a GB200: the example boots VisualGen with warmup skipped, prints all four introspection sections, generates, and saves a valid 832x480 / 101-frame / 16 fps H.264 AVI to disk.
• Sphinx make html builds clean with no new warnings on api_walkthrough.rst / visual_gen_examples.rst; the "VisualGen Examples" entry shows up between LLM Examples and Online Serving Examples in the side nav.

PR Checklist

Please review the following before submitting your PR:

• PR description clearly explains what and why. If using CodeRabbit's summary, please make sure it makes sense.
• PR Follows TRT-LLM CODING GUIDELINES to the best of your knowledge.
• Test cases are provided for new code paths (see test instructions)
• If PR introduces API changes, an appropriate PR label is added - either api-compatible or api-breaking. For api-breaking, include BREAKING in the PR title.
• Any new dependencies have been scanned for license and vulnerabilities
• CODEOWNERS updated if ownership changes
• Documentation updated as needed
• Update tava architecture diagram if there is a significant design change in PR.
• The reviewers assigned automatically/manually are appropriate for the PR.
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Summary by CodeRabbit

• New Features

  • Added a VisualGen API example demonstrating end-to-end usage including model selection, pipeline configuration, parameter customization, and video generation with output saving.

• Documentation

  • Expanded documentation to include VisualGen example resources and updated the main documentation index.

• Tests

  • Added integration test for VisualGen API walkthrough across multiple GPU configurations.

[zhenhuaw-me]

/bot run

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds a VisualGen API example script with full documentation and integration testing. The changes update documentation generation to produce VisualGen example docs, integrate them into the main index, implement the example walkthrough, add an integration test to validate it, and register the test across multiple GPU test matrices.

Changes

VisualGen API Walkthrough Example

Layer / File(s)	Summary
Documentation generation for VisualGen examples docs/source/helper.py	Updated generate_examples() to collect scripts from examples/visual_gen, expanded the ignore list with VisualGen-specific entries and comments, and generate a dedicated visual_gen_examples.rst toctree.
Documentation index integration docs/source/index.rst	Added the generated examples/visual_gen_examples.rst to the "Deployment Guide" toctree.
VisualGen API walkthrough example script examples/visual_gen/api_walkthrough.py	New example demonstrating end-to-end VisualGen API usage: lists supported models, retrieves pipeline config, constructs VisualGen instance with compilation config, inspects extra param specs, builds and overrides request parameters, generates media output, and saves to AVI.
Integration test for API walkthrough example tests/integration/defs/examples/test_visual_gen.py	Added test_visual_gen_api_walkthrough that verifies the example runs successfully by checking for the Wan 2.1 T2V model, symlinking the checkpoint into venv workspace, executing the example script, and asserting the .avi output is produced.
Test matrix registration across GPU configurations tests/integration/test_lists/test-db/l0_dgx_b200.yml, l0_gh200.yml, l0_h100.yml, l0_l40s.yml	Registered test_visual_gen_api_walkthrough in four GPU-specific test matrices under their respective condition blocks.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Suggested reviewers

• QiJune

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically summarizes the main changes: adding a VisualGen API walkthrough example and corresponding documentation page.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The PR description comprehensively explains the changes, including the new API walkthrough example, documentation integration, test coverage, and verification details.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

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[coderabbitai]

Actionable comments posted: 2

🧹 Nitpick comments (1)

tests/integration/defs/examples/test_visual_gen.py (1)

1177-1197: Coverage is sufficient for this new example path.

tests/integration/defs/examples/test_visual_gen.py::test_visual_gen_api_walkthrough validates execution + output artifact, and the PR also wires it into tests/integration/test_lists/test-db/l0_dgx_b200.yml, tests/integration/test_lists/test-db/l0_gh200.yml, tests/integration/test_lists/test-db/l0_h100.yml, and tests/integration/test_lists/test-db/l0_l40s.yml.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@tests/integration/defs/examples/test_visual_gen.py` around lines 1177 - 1197,
The test test_visual_gen_api_walkthrough manipulates model_dst by creating
directories and a symlink but doesn't guard against an existing non-symlink
destination nor perform cleanup, which can cause flaky runs; update the test to
(1) if model_dst exists and is not a symlink, fail or skip with a clear message,
(2) create the parent dirs and symlink only when model_dst is absent, and (3)
remove the created symlink (and any empty parent dir you created) in a
finally/teardown block after venv_check_call finishes; reference model_src,
model_dst, venv_check_call and output_path when making these changes.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@examples/visual_gen/api_walkthrough.py`:
- Line 7: The function main is missing an explicit return type annotation;
update the definition of main in api_walkthrough.py to include a return type
(e.g., def main() -> None:) since this module requires all functions be
annotated — ensure the signature uses -> None if it does not return a value and
adjust any callers if you change the contract.
- Around line 1-4: This new module is missing the required NVIDIA SPDX
copyright/license header; add the standard NVIDIA SPDX header block at the very
top of the file before any metadata or imports so the file begins with the
license text followed by the existing lines that import VisualGen,
VisualGenArgs, and CompilationConfig; ensure the exact company and SPDX
identifier used across the repo is used verbatim and that the header precedes
the "### :title" metadata and the imports.

---

Nitpick comments:
In `@tests/integration/defs/examples/test_visual_gen.py`:
- Around line 1177-1197: The test test_visual_gen_api_walkthrough manipulates
model_dst by creating directories and a symlink but doesn't guard against an
existing non-symlink destination nor perform cleanup, which can cause flaky
runs; update the test to (1) if model_dst exists and is not a symlink, fail or
skip with a clear message, (2) create the parent dirs and symlink only when
model_dst is absent, and (3) remove the created symlink (and any empty parent
dir you created) in a finally/teardown block after venv_check_call finishes;
reference model_src, model_dst, venv_check_call and output_path when making
these changes.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Enterprise

Run ID: 8e95a48d-d9e2-4388-a0e8-d8bb32cb22de

📥 Commits

Reviewing files that changed from the base of the PR and between e73d068 and e6ba49b.

📒 Files selected for processing (8)

• docs/source/helper.py
• docs/source/index.rst
• examples/visual_gen/api_walkthrough.py
• tests/integration/defs/examples/test_visual_gen.py
• tests/integration/test_lists/test-db/l0_dgx_b200.yml
• tests/integration/test_lists/test-db/l0_gh200.yml
• tests/integration/test_lists/test-db/l0_h100.yml
• tests/integration/test_lists/test-db/l0_l40s.yml

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[karljang]

LGTM!