cp: docs: Update callback code snippets to include all imports needed for example (2283) into r0.3.0

[ko3n1g]

beep boop [🤖]: Hi @ananthsub 👋,

we've cherry picked #2283 into  for you! 🚀

Please review and approve this cherry pick by your convenience!

Summary by CodeRabbit

• Documentation
  • Updated training callbacks documentation with improved examples demonstrating class-based callbacks, functional callbacks, and combined pattern approaches for model training workflows.

[ko3n1g]

/ok to test 11c6a55

[copy-pr-bot]

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[coderabbitai]

📝 Walkthrough

Walkthrough

Updates documentation examples in the callbacks guide to use new imports (time, forward_step, qwen25_500m_pretrain_config) and replace forward_step_func with forward_step, adding config instantiation across multiple example sections.

Changes

Cohort / File(s)	Summary
Documentation Updates docs/training/callbacks.md	Updated callback examples across three sections (Quick Start, Functional Callbacks, Mixing Both Patterns) to include new imports (time, forward_step, qwen25_500m_pretrain_config), replace forward_step_func with forward_step, and add config instantiation (config = qwen25_500m_pretrain_config()).

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Possibly related PRs

• docs: Update callback code snippets to include all imports needed for example #2283: Makes identical documentation updates to docs/training/callbacks.md with the same import additions, function name replacements, and config instantiation changes across callback examples.

Suggested labels

documentation, docs-only, r0.3.0

Suggested reviewers

• yaoyu-33

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: updating callback code snippets in documentation to include all necessary imports, with a reference to the original PR #2283.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Test Results For Major Changes	✅ Passed	This PR contains only minor documentation updates to code examples in docs/training/callbacks.md, with no impact on runtime behavior or functionality.

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch cherry-pick-2283-r0.3.0

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@docs/training/callbacks.md`:
- Around line 67-82: The example uses undefined callback classes (MyCallback,
TimingCallback, MetricsCallback) when creating CallbackManager and calling
manager.add/register; update the snippet to be self-contained by either
importing/defining the referenced callbacks or adding a short inline comment
above the manager.add calls stating these are placeholder/example callback names
that must be defined or imported by the user (e.g., "Assuming
MyCallback/TimingCallback/MetricsCallback are defined elsewhere"), and ensure
references to CallbackManager, manager.add, and manager.register remain correct.

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

Documentation clarity: code example is not self-contained.

This code block references MyCallback(), TimingCallback(), and MetricsCallback() (line 74-75) but none of these are defined or imported in this example. While MyCallback is defined in the first example, TimingCallback and MetricsCallback are not defined anywhere in this document.

For better documentation, consider either:

1. Adding a comment noting these are example callback names and users should define them
2. Importing or defining these callbacks in the example
3. Using simpler inline examples that don't reference undefined classes

📝 Suggested improvement for clarity

 ```python
 from megatron.bridge.training.callbacks import CallbackManager
 from megatron.bridge.training.gpt_step import forward_step
 from megatron.bridge.training.pretrain import pretrain
 from megatron.bridge.recipes.qwen import qwen25_500m_pretrain_config

+# Assuming MyCallback is defined as shown in the Quick Start example above
+# and you have defined TimingCallback and MetricsCallback for your use case
+
 manager = CallbackManager()
 manager.add(MyCallback())
-manager.add([TimingCallback(), MetricsCallback()])
+manager.add([MyOtherCallback()])  # Add any other callback instances
 manager.register("on_eval_end", lambda ctx: print("Evaluation complete!"))

🤖 Prompt for AI Agents

In `@docs/training/callbacks.md` around lines 67 - 82, The example uses undefined
callback classes (MyCallback, TimingCallback, MetricsCallback) when creating
CallbackManager and calling manager.add/register; update the snippet to be
self-contained by either importing/defining the referenced callbacks or adding a
short inline comment above the manager.add calls stating these are
placeholder/example callback names that must be defined or imported by the user
(e.g., "Assuming MyCallback/TimingCallback/MetricsCallback are defined
elsewhere"), and ensure references to CallbackManager, manager.add, and
manager.register remain correct.