Add safetensor option when saving and restoring models
I just wanted to chime in that if there is any way to get this pull request merged into the main branch and a release branch that would be hugely helpful.  I can hobble along using my clone of this branch, but that's obviously not ideal.  Thank you guys for you great work and for this really helpful contribution in particular! This PR is stale because it has been open for 14 days with no activity. Remove stale label or comment or update or this will be closed in 7 days. This PR was closed because it has been inactive for 7 days since being marked as stale. Reopened. It got stale over the holidays. I just wanted to say I fully endorse this pull request.  I tested it and it works well for my use case.  It will greatly enable my work if some form of this safetensor PR can make it into the main branch.  Thank you!!! <!-- 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.asr.models.clustering_diarizer
nemo/collections/asr/models/clustering_diarizer.py:238:0: C0301: Line too long (135/119) (line-too-long)
nemo/collections/asr/models/clustering_diarizer.py:242:0: C0301: Line too long (164/119) (line-too-long)
nemo/collections/asr/models/clustering_diarizer.py:328:0: C0301: Line too long (121/119) (line-too-long)
nemo/collections/asr/models/clustering_diarizer.py:549:4: C0116: Missing function or method docstring (missing-function-docstring)
************* Module nemo.collections.asr.modules.audio_preprocessing
nemo/collections/asr/modules/audio_preprocessing.py:98:0: C0301: Line too long (667/119) (line-too-long)
nemo/collections/asr/modules/audio_preprocessing.py:95:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/audio_preprocessing.py:106:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/audio_preprocessing.py:304:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/audio_preprocessing.py:545:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/audio_preprocessing.py:616:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/audio_preprocessing.py:667:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/audio_preprocessing.py:724:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/modules/audio_preprocessing.py:757:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/modules/audio_preprocessing.py:776:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/modules/audio_preprocessing.py:792:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/modules/audio_preprocessing.py:798:0: C0115: Missing class docstring (missing-class-docstring)
************* Module nemo.collections.asr.modules.conv_asr
nemo/collections/asr/modules/conv_asr.py:197:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/conv_asr.py:239:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/conv_asr.py:399:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/conv_asr.py:459:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/conv_asr.py:503:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/conv_asr.py:507:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/conv_asr.py:603:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/conv_asr.py:677:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/conv_asr.py:689:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/conv_asr.py:758:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/conv_asr.py:858:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/conv_asr.py:881:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/modules/conv_asr.py:900:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/modules/conv_asr.py:945:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/modules/conv_asr.py:969:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/modules/conv_asr.py:983:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/modules/conv_asr.py:992:0: C0115: Missing class docstring (missing-class-docstring)
************* Module nemo.collections.nlp.models.nlp_model
nemo/collections/nlp/models/nlp_model.py:187:0: C0301: Line too long (121/119) (line-too-long)
nemo/collections/nlp/models/nlp_model.py:191:0: C0301: Line too long (120/119) (line-too-long)
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nemo/collections/nlp/models/nlp_model.py:454:4: C0116: Missing function or method docstring (missing-function-docstring)
************* Module nemo.collections.nlp.parts.nlp_overrides
nemo/collections/nlp/parts/nlp_overrides.py:212:0: C0301: Line too long (140/119) (line-too-long)
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nemo/collections/nlp/parts/nlp_overrides.py:248:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/nlp/parts/nlp_overrides.py:381:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/nlp/parts/nlp_overrides.py:425:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/nlp/parts/nlp_overrides.py:602:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/nlp/parts/nlp_overrides.py:618:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/nlp/parts/nlp_overrides.py:637:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/nlp/parts/nlp_overrides.py:878:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/nlp/parts/nlp_overrides.py:997:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/nlp/parts/nlp_overrides.py:1689:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/nlp/parts/nlp_overrides.py:1777:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/nlp/parts/nlp_overrides.py:18:0: W0611: Unused import re (unused-import)
nemo/collections/nlp/parts/nlp_overrides.py:106:4: W0611: Unused tensorstore imported from megatron.core.dist_checkpointing.strategies (unused-import)
************* Module nemo.core.classes.common
nemo/core/classes/common.py:693:0: C0301: Line too long (120/119) (line-too-long)
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nemo/core/classes/common.py:471:0: C0115: Missing class docstring (missing-class-docstring)
nemo/core/classes/common.py:567:0: C0115: Missing class docstring (missing-class-docstring)
nemo/core/classes/common.py:647:0: C0115: Missing class docstring (missing-class-docstring)
nemo/core/classes/common.py:1026:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/common.py:1141:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/common.py:29:0: W0611: Unused Iterable imported from typing (unused-import)
************* Module nemo.core.classes.modelPT
nemo/core/classes/modelPT.py:82:0: C0301: Line too long (130/119) (line-too-long)
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nemo/core/classes/modelPT.py:223:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/modelPT.py:878:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/modelPT.py:944:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/modelPT.py:948:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/modelPT.py:955:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/modelPT.py:1223:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/modelPT.py:1647:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/classes/modelPT.py:1765:4: C0116: Missing function or method docstring (missing-function-docstring)
************* Module nemo.core.connectors.save_restore_connector
nemo/core/connectors/save_restore_connector.py:51:0: C0301: Line too long (135/119) (line-too-long)
nemo/core/connectors/save_restore_connector.py:208:0: C0301: Line too long (141/119) (line-too-long)
nemo/core/connectors/save_restore_connector.py:315:0: C0301: Line too long (140/119) (line-too-long)
nemo/core/connectors/save_restore_connector.py:430:0: C0301: Line too long (141/119) (line-too-long)
nemo/core/connectors/save_restore_connector.py:435:0: C0301: Line too long (141/119) (line-too-long)
nemo/core/connectors/save_restore_connector.py:38:0: C0115: Missing class docstring (missing-class-docstring)
nemo/core/connectors/save_restore_connector.py:704:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/connectors/save_restore_connector.py:712:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/connectors/save_restore_connector.py:720:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/core/connectors/save_restore_connector.py:728:4: C0116: Missing function or method docstring (missing-function-docstring)

-----------------------------------
Your code has been rated at 9.75/10
```

---

Mitigation guide:

* Add sensible and useful docstrings to functions and methods
* For trivial methods like getter/setters, consider adding `# pylint: disable=C0116` inside the function itself
* To disable multiple functions/methods at once, put a `# pylint: disable=C0116` before the first and a `# pylint: enable=C0116` after the last.

By applying these rules, we reduce the occurance of this message in future.

Thank you for improving NeMo's documentation!
# What does this PR do ?

Re-do changes in a previously closed PR https://github.com/NVIDIA/NeMo/pull/7812 to add safetensor options when saving and restoring models. as customers requested.

CC @galv 

**Collection**: [core,asr,nlp,common]

# Changelog 
- Re-do changes in https://github.com/NVIDIA/NeMo/pull/7812 for current main branch
- add nemo.utils.secure.torch_load and nemo.utils.secure.torch_save
- torch.load and torch.save removed from save_restore_connector and alternates of it
- secure.torch_load and torch_save use safetensors when available, however if safe=False torch.load and torch.save are used to allow for backwards compatability
 - safe is a named parameter and passed through from save_to and restore_from. The default is safe=False to preserve backwards compatability
- added unit tests to double check backwards compatability and secure functions work correctly.

# Usage

Following usage is copied from https://github.com/NVIDIA/NeMo/pull/7812

When using nemo with untrusted .nemo files this will greatly reduce the potential for the user to be attacked.
```
# Existing usage should be preserved. although the result will include a .safetensor inside the .nemo now as well
model.save_to(save_path=model_save_path)
model.save_to(save_path=model_save_path, safe=False)

# the .nemo will only include the .safetensor.
model.save_to(save_path=model_save_path, safe=True)

# Existing usage should be preserved. although if the .nemo contains a .safetensor, it will be used instead of the pytorch version
model.restore_from(model_save_path)
model.restore_from(save_path=model_save_path, safe=False)

# The restore will fail if a .safetensor isn't available to prevent an untrusted .nemo file from resulting in an exploit
model.restore_from(save_path=model_save_path, safe=True)
```


**PR Type**:
- [x] New Feature
- [ ] Bugfix
- [ ] Documentation
