docs: Update callback code snippets to include all imports needed for example

[ananthsub]

What does this PR do ?

Update callback docs to be directly runnable if copy/pasting the code snippet

Changelog

• Add specific line by line info of high level changes in this PR.

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Additional Information

• Related to # (issue)

Summary by CodeRabbit

• Documentation
  • Updated training callback docs with refreshed examples that follow the current API, including how to create and pass configurations and callbacks.
  • Added on-trace usage examples and updated example import lines for clarity.
  • Clarified examples only—no runtime or public API behavior changed.

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[ananthsub]

/ok to test 7777851

[coderabbitai]

📝 Walkthrough

Walkthrough

Documentation examples in docs/training/callbacks.md updated to import and use forward_step from megatron.bridge.training.gpt_step, replace forward_step_func occurrences, and switch example config usage to qwen25_500m_pretrain_config with adjusted pretrain call signatures.

Changes

Cohort / File(s)	Summary
Training Documentation docs/training/callbacks.md	Updated example snippets to import forward_step from megatron.bridge.training.gpt_step, replace forward_step_func references with forward_step, add imports for qwen25_500m_pretrain_config, and adjust pretrain example call signatures to pass the new config and callbacks.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• Add callbacks to finetune function #2278 — Adds a callbacks parameter to finetune and forwards it to pretrain, touching the same pretrain/callbacks flow that documentation examples now illustrate.

🚥 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 accurately reflects the main change: updating callback documentation code snippets to include necessary imports for runnable examples.
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 pull request contains only minor documentation changes that update callback code snippets with necessary imports. No code logic or functionality is affected.

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[coderabbitai]

Actionable comments posted: 1

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

docs/training/callbacks.md (1)

3-3: ⚠️ Potential issue | 🟡 Minor

Fix typo in intro sentence.

“propietary” → “proprietary”.

🤖 Fix all issues with AI agents

In `@docs/training/callbacks.md`:
- Around line 67-82: The example uses undefined callbacks (MyCallback,
TimingCallback, MetricsCallback) which breaks copy‑paste; update the code block
to include minimal in‑block callback definitions or replace their usages with
simple inline callbacks that implement the expected interface used by
CallbackManager (e.g., define a small class MyCallback with the relevant hook
methods or add lambdas/anonymous functions) so the snippet from CallbackManager,
manager.register(...), and pretrain(config, forward_step, callbacks=manager) is
fully runnable without external imports.

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

Mixing example still isn’t copy‑paste runnable.

This snippet references MyCallback, TimingCallback, and MetricsCallback without definitions/imports in the block. Given the PR objective (“directly runnable when copy/pasted”), please either add minimal class definitions in this block or replace with fully in‑block example callbacks.

🤖 Prompt for AI Agents

In `@docs/training/callbacks.md` around lines 67 - 82, The example uses undefined
callbacks (MyCallback, TimingCallback, MetricsCallback) which breaks copy‑paste;
update the code block to include minimal in‑block callback definitions or
replace their usages with simple inline callbacks that implement the expected
interface used by CallbackManager (e.g., define a small class MyCallback with
the relevant hook methods or add lambdas/anonymous functions) so the snippet
from CallbackManager, manager.register(...), and pretrain(config, forward_step,
callbacks=manager) is fully runnable without external imports.

[ananthsub]

/ok to test 91d28d7