Validate CelebA target_type in __init__ using verify_str_arg

[sunnycho100]

Motivation

There's a long-standing TODO comment in CelebA.__getitem__() (line ~189):

# TODO: refactor with utils.verify_str_arg

Currently, invalid target_type values are only caught at __getitem__ time via a raw ValueError. Meanwhile, the split parameter is already validated in __init__() using verify_str_arg. This inconsistency means users don't get an error until they try to access an item, even though the problem is known at construction time.

Changes

torchvision/datasets/celeba.py

• Added verify_str_arg validation for each entry in target_type inside __init__(), right after the list normalization — same pattern already used for split
• Removed the now-unreachable else branch (and the TODO) from __getitem__()

Before / After

# Before — error only at item access time
ds = CelebA(root, target_type="typo")  # no error
ds[0]  # ValueError: Target type "typo" is not recognized.

# After — error immediately at construction
ds = CelebA(root, target_type="typo")
# ValueError: Unknown value 'typo' for argument target_type.
#   Valid values are {'attr', 'identity', 'bbox', 'landmarks'}.

Notes

• Fully backward-compatible — only changes when the error is raised, not what is accepted
• No new dependencies — verify_str_arg is already imported in the file

[pytorch-bot]

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[zy1git]

@sunnycho100 Thanks a lot for this PR! After discussion, we won’t be merging it as-is since it isn’t a current priority for TorchVision.
If you update this PR to only remove the # TODO: refactor with utils.verify_str_arg comment and adjust the PR description accordingly, I’m happy to approve and merge it.