Add unit test for ArrowDataset

[cih9088]

Summary

A following work of #931

• Added unit test for ArrowDataset.__getitem__.
• Fixed typo.

How to test

Checklist

• I have added unit tests to cover my changes.​
• I have added integration tests to cover my changes.​
• I have added the description of my changes into CHANGELOG.​
• I have updated the documentation accordingly

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.
• I have updated the license header for each file (see an example below).

# Copyright (C) 2023 Intel Corporation
#
# SPDX-License-Identifier: MIT

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.08 🎉

Comparison is base (eaae1e1) 78.65% compared to head (eeb8d8e) 78.73%.

Additional details and impacted files

@@                Coverage Diff                 @@
##           releases/1.2.0     #934      +/-   ##
==================================================
+ Coverage           78.65%   78.73%   +0.08%     
==================================================
  Files                 228      228              
  Lines               26342    26344       +2     
  Branches             5249     5250       +1     
==================================================
+ Hits                20718    20742      +24     
+ Misses               4406     4385      -21     
+ Partials             1218     1217       -1     

Flag	Coverage Δ
macos-11_Python-3.8	77.75% <100.00%> (+0.08%)	⬆️
ubuntu-20.04_Python-3.8	78.71% <100.00%> (+0.08%)	⬆️
windows-2019_Python-3.8	78.61% <100.00%> (+0.08%)	⬆️

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

Impacted Files	Coverage Δ
datumaro/components/progress_reporting.py	61.53% <ø> (ø)
...tumaro/plugins/data_formats/arrow/arrow_dataset.py	81.61% <100.00%> (+16.69%)	⬆️

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[vinnamkim]

LGTM.