Fix datasets

Fix datasets

Description

Wants to merge: fix/datasets_links into main

Type of change

• Bug fix
• New feature
• Enhancement
• Documentation update
• Other (specify right below)

Merge request commits

• Fix dataset links, slightly refactor

Fix some issues with the datasets:

• fix wikitext103 dead link
• fix tinystories correct link (it now results in exactly the same dataset as the one obtained via huggingface's load_dataset() interface)
• reduce the number of splits (from ['train', 'test', 'valid'] to ['train', 'test']) for all datasets
• add extract_tgz() method to dataset utils

Related Issues

Screenshots or GIFs

Checklist

• I have tested the code with the changes manually.
• My code follows the project's style guidelines.
• I have documented my code for others to understand.
• I have updated documentation as needed (including README.md, code comments and doc strings).

Reviewer Guidelines

Additional Notes

@mentions