draft: alternative packed seq format to prevent memory blow
State: open | Pull request: yes
Labels: name: NLP

# What does this PR do ?

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**Collection**: [Note which collection this PR will affect]

# Changelog 
- Add specific line by line info of high level changes in this PR.

# Usage
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```python
# Add a code snippet demonstrating how to use this 
```

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# Additional Information
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<!-- 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.nlp.data.language_modeling.megatron.gpt_sft_dataset
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:76:0: C0301: Line too long (353/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:78:0: C0301: Line too long (173/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:79:0: C0301: Line too long (156/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:85:0: C0301: Line too long (157/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:88:0: C0301: Line too long (147/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:89:0: C0301: Line too long (178/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:90:0: C0301: Line too long (138/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:91:0: C0301: Line too long (121/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:93:0: C0301: Line too long (144/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:96:0: C0301: Line too long (247/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:171:0: C0301: Line too long (125/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:180:0: C0301: Line too long (121/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:250:0: C0301: Line too long (137/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:253:0: C0301: Line too long (133/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:278:0: C0301: Line too long (146/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:283:0: C0301: Line too long (153/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:284:0: C0301: Line too long (155/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:306:0: C0301: Line too long (127/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:395:0: C0301: Line too long (120/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:723:0: C0301: Line too long (120/119) (line-too-long)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:42:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/nlp/data/language_modeling/megatron/gpt_sft_dataset.py:546:0: C0115: Missing class docstring (missing-class-docstring)

-----------------------------------
Your code has been rated at 9.39/10
```

---

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

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