MegatronStrategy: make pipeline_dtype function attribute.
State: closed | Pull request: yes
Labels: name: Run CICD

# What does this PR do ?

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# Additional Information
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[🤖]: Hi @akoumpa 👋,

We wanted to let you know that a [CICD pipeline](https://github.com/NVIDIA/NeMo/actions/runs/12241618845) for this PR just finished successfully

So it might be time to merge this PR or get some approvals

I'm just a bot so I'll leave it you what to do next.

//cc @pablo-garay @ko3n1g

<!-- pylint-output-strict-mode-false -->

beep boop 🤖: 🙏 The following files have warnings. In case you are familiar with these, please try helping us to improve the code base.

---

Your code was analyzed with PyLint. The following annotations have been identified:

```
************* Module nemo.collections.llm.api
nemo/collections/llm/api.py:604:0: C0116: Missing function or method docstring (missing-function-docstring)
************* Module nemo.lightning.pytorch.strategies.megatron_strategy
nemo/lightning/pytorch/strategies/megatron_strategy.py:282:4: C0116: Missing function or method docstring (missing-function-docstring)

-----------------------------------
Your code has been rated at 9.97/10
```

---

Thank you for improving NeMo's documentation!

<!-- pylint-output-strict-mode-false -->

beep boop 🤖: 🙏 The following files have warnings. In case you are familiar with these, please try helping us to improve the code base.

---

Your code was analyzed with PyLint. The following annotations have been identified:

```
************* Module nemo.collections.llm.api
nemo/collections/llm/api.py:604:0: C0116: Missing function or method docstring (missing-function-docstring)
************* Module nemo.lightning.pytorch.strategies.megatron_strategy
nemo/lightning/pytorch/strategies/megatron_strategy.py:282:4: C0116: Missing function or method docstring (missing-function-docstring)

-----------------------------------
Your code has been rated at 9.97/10
```

---

Thank you for improving NeMo's documentation!

[🤖]: Hi @akoumpa 👋,

We wanted to let you know that a [CICD pipeline](https://github.com/NVIDIA/NeMo/actions/runs/12250230260) for this PR just finished successfully

So it might be time to merge this PR or get some approvals

I'm just a bot so I'll leave it you what to do next.

//cc @pablo-garay @ko3n1g