Fix trainer.fit docstring render bug

[ritoban23]

What does this PR do?

Fixes a documentation rendering bug in trainer.fit where :rtype: None was incorrectly displayed.

Fixes #21356

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---

📚 Documentation preview 📚: https://pytorch-lightning--21362.org.readthedocs.build/en/21362/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79%. Comparing base (f7692a6) to head (9664830).
⚠️ Report is 1 commits behind head on master.
✅ All tests successful. No failed tests found.

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HEAD has 125 uploads less than BASE

Flag	BASE (f7692a6)	HEAD (9664830)
cpu	60	29
lightning	30	14
pytest	30	0
python3.11	12	6
python3.10	6	2
lightning_fabric	15	0
python3.12	18	9
python3.12.7	18	9
python	6	3
pytorch2.1	6	5
pytest-full	30	29

Additional details and impacted files

@@            Coverage Diff            @@
##           master   #21362     +/-   ##
=========================================
- Coverage      87%      79%     -8%     
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  Files         269      266      -3     
  Lines       23765    23710     -55     
=========================================
- Hits        20591    18693   -1898     
- Misses       3174     5017   +1843     

[deependujha]

Hi @ritoban23, thanks for choosing to make PyTorch Lightning more awesome. Can you please look at failing doc tests?

[turbotimon]

I'm wondering why the note is necessary and why it is not the same issue e.g. here:

pytorch-lightning/src/lightning/pytorch/trainer/trainer.py

Line 924 in a4315bf

See :ref:`Lightning inference section<deploy/production_basic:Predict step with your LightningModule>` for more.

However, it may would fix the problem and be more concise to just move the "For more.." sentence up, just below the parameters, like it is done in validate, test and predict:

pytorch-lightning/src/lightning/pytorch/trainer/trainer.py

Lines 663 to 677 in a4315bf

	weights_only: Defaults to ``None``. If ``True``, restricts loading to ``state_dicts`` of plain
	``torch.Tensor`` and other primitive types. If loading a checkpoint from a trusted source that contains
	an ``nn.Module``, use ``weights_only=False``. If loading checkpoint from an untrusted source, we
	recommend using ``weights_only=True``. For more information, please refer to the
	`PyTorch Developer Notes on Serialization Semantics <https://docs.pytorch.org/docs/main/notes/serialization.html#id3>`_.
	For more information about multiple dataloaders, see this :ref:`section <multiple-dataloaders>`.
	Returns:
	List of dictionaries with metrics logged during the validation phase, e.g., in model- or callback hooks
	like :meth:`~lightning.pytorch.LightningModule.validation_step` etc.
	The length of the list corresponds to the number of validation dataloaders used.
	Raises:
	TypeError:

[bhimrazy]

However, it may would fix the problem and be more concise to just move the "For more.." sentence up, just below the parameters, like it is done in validate, test and predict:

Agreed, @turbotimon. Ideally this text should appear right after the parameters. The tricky part seems to be that the Returns section gets auto-inserted in between, which seems to prevent placing it exactly where we want.