[Feature] Support Stanford Cars dataset.

[zzc98]

Motivation

Support Stanford Car dataset .

Example

>>> from mmcls.data import StanfordCars

>>> data_root = 'data/stanfordcars'
>>> train=StanfordCars(data_prefix=data_root, test_mode=False, pipeline=[])
>>> len(train)
8144
>>> val = StanfordCars(data_prefix=data_root, test_mode=True, pipeline=[])
>>> len(val)
8041

Checklist

Before PR:

• Pre-commit or other linting tools are used to fix the potential lint issues.
• Bug fixes are fully covered by unit tests, the case that causes the bug should be added in the unit tests.
• The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, like docstring or example tutorials.

After PR:

• If the modification has potential influence on downstream or other related projects, this PR should be tested with those projects, like MMDet or MMSeg.
• CLA has been signed and all committers have signed the CLA in this PR.

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #893 (37f0469) into dev (e54cfd6) will increase coverage by 0.03%.
The diff coverage is 94.28%.

❗ Current head 37f0469 differs from pull request most recent head 22b479f. Consider uploading reports for the commit 22b479f to get more accurate results

@@            Coverage Diff             @@
##              dev     #893      +/-   ##
==========================================
+ Coverage   85.86%   85.90%   +0.03%     
==========================================
  Files         137      138       +1     
  Lines        9363     9398      +35     
  Branches     1621     1627       +6     
==========================================
+ Hits         8040     8073      +33     
- Misses       1082     1084       +2     
  Partials      241      241              

Flag	Coverage Δ
unittests	85.82% <94.28%> (+0.03%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mmcls/datasets/stanford_cars.py	94.11% <94.11%> (ø)
mmcls/datasets/__init__.py	100.00% <100.00%> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[Ezra-Yu]

LGTM.

[mzr1996]

Please move the scipy to the optional requirement file.

[mzr1996]

Please import scipy.io only when using it. The scipy package is a little large, and if we only use it in a dataset class, don't make it a required package.

[mzr1996]

Same in the unit tests.

[OpenMMLab-Assistant001]

Hi @zzc98 ！First of all, we want to express our gratitude for your significant PR in the MMClassification project. Your contribution is highly appreciated, and we are grateful for your efforts in helping improve this open-source project during your personal time. We believe that many developers will benefit from your PR

We would also like to invite you to join our Special Interest Group (SIG) private channel on Discord, where you can share your experiences, ideas, and build connections with like-minded peers. To join the SIG channel, simply message moderator— OpenMMLab on Discord or briefly share your open-source contributions in the #introductions channel and we will assist you. Look forward to seeing you there! Join us ：https://discord.gg/UjgXkPWNqA

If you have WeChat account，welcome to join our community on WeChat. You can add our assistant ：openmmlabwx. Please add "mmsig + Github ID" as a remark when adding friends：）
Thank you again for your contribution！❤