Add UnlabeledImageDataset

[C-you-know]

Closes #9050

Adds UnlabeledImageDataset: a generic loader for unlabeled images discovered via glob patterns, for unsupervised/self-supervised use where there's no per-class folder layout. getitem returns just the image, not a (sample, target) tuple.

• Default patterns match all IMG_EXTENSIONS recursively, in both lower- and upper-case (so discovery is consistent on case-sensitive filesystems), deduped and sorted.
• self.samples stores str paths, matching ImageFolder.
• Tests cover default/custom patterns, uppercase discovery, sort/uniqueness, the bare-image return, transforms, custom loader, pathlib root, and the not-found cases.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/vision/9645

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

This comment was automatically generated by Dr. CI and updates every 15 minutes.

[meta-cla]

Hi @C-you-know!

Thank you for your pull request and welcome to our community.

Action Required

In order to merge any pull request (code, docs, etc.), we require contributors to sign our Contributor License Agreement, and we don't seem to have one on file for you.

Process

In order for us to review and merge your suggested changes, please sign at https://code.facebook.com/cla. If you are contributing on behalf of someone else (eg your employer), the individual CLA may not be sufficient and your employer may need to sign the corporate CLA.

Once the CLA is signed, our tooling will perform checks and validations. Afterwards, the pull request will be tagged with CLA signed. The tagging process may take up to 1 hour after signing. Please give it that time before contacting us about it.

If you have received this in error or have any questions, please contact us at cla@meta.com. Thanks!

[meta-cla]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Meta Open Source project. Thanks!

[C-you-know]

Gentle Ping @NicolasHug 🙂